Det 20. Landsmøte i kjemi

Posters og Posterabstracts

Disse faggruppene har postere:

PU - Uorganisk kjemi og materialkjemi

PK - Kvantekjemi og modellering

Abstractene står under titlene

PU - Uorganisk kjemi og materialkjemi

Abstracts

PU1

A new approach for correcting transport numbers of native and foreign ions in molten carbonates

¹Anna Evans, Wen Xing², Marie-Laure Fontaine², Thijs Peters², Rune Bredesen², Truls Norby¹

¹Department of Chemistry, University of Oslo, Oslo, Norway
²SINTEF Materials and Chemistry, Oslo, Norway

Dual-phase membranes consisting of a molten carbonate phase embedded in a porous ceramic matrix were recently suggested for CO₂ separation at 500-700 ˚C [1-3]. The combination of a carbonate-ion conductor and an oxide-ion conductor can be used to achieve ambipolar transport of CO₂, and thus capture CO₂ with high selectivity. However, a detailed understanding of the transport mechanism of CO₂ through this dual-phase structure is still missing.

In this study, electromotive force (EMF) measurements were performed in selected operating conditions on dual-phase membranes consisting of a eutectic Li-Na-K carbonate and a porous alumina framework. The voltage across the molten phase was measured under activity gradients of CO₂, O₂ and/or H₂O in the temperature range of 450-600 °C. Electrochemical impedance spectra were collected in order to be able to correct for the electrode polarisation in the transport numbers. A new approach was developed for correcting transport numbers of native ions (CO₃^2–, Li⁺, Na⁺, K⁺) that takes into account the electrode polarisation of foreign ions (O^2– and/or OH^–).

Results show that the corrected transport numbers for the sum of native CO₃^2- and alkali metal cations were found to be close to unity in a gradient of pCO₂. In an activity gradient pH₂O, evidence for the transport of hydroxide ions was detected.

References

1.      S.G. Patrício, et al., J. Membr. Sci. (2014).

2.      M.L. Fontaine, et al., Energy Proc. (2013).

3.      J.L. Wade, et al., J. Membr. Sci. (2011).

PU2

A first-principles study of epitaxial interfaces between graphene and GaAs

Astrid Marthinsen, Gerhard Olsen, Sverre Magnus Selbach

 
Department of Materials Science and Engineering, NTNU

 
Epitaxial interfaces between graphene and GaAs(111) have been investigated through a first-principles study using density functional theory (DFT) [1]. GaAs(111) nanowires have been successfully grown on graphene [2] and are highly promising for flexible opto-electronics.

A computational model to describe the possible configurations and to investigate interactions at the interface has been constructed. The GaAs(111) surface at the interface is assumed to be reconstructed with Ga vacancies. Three different relative phase orientations between the GaAs(111) surface and graphene have been studied; , , , respectively, where three different translations of the configuration have been considered. Within the three considered epitaxial phase orientations, the GaAs phase is strained in the (111) plane to accommodate a lattice mismatch of 6.3%, 10% and -8.2% in the , and the orientations, respectively. Biaxial straining of bulk GaAs have been studied, both in the zinkblende (ZB) phase ((111) plane) and in the meta-stable wurtzite (WZ) phase ((0001) plane). The relative stabilities of the two phases are found to depend on the degree of strain. Biaxial straining of GaAs(111) surfaces have also been investigated. The surface reconstruction energy is highly dependent on the degree of strain for GaAs(111) - reconstructed surfaces.

The interactions between GaAs and graphene at the interface have been studied by two different exchange-correlation functionals: The semi-local GGA functional PBEsol, and the van der Waals (vdW) functional optPBE. The latter is found to yield a significantly stronger interaction energy, which signifies a substantial vdW contribution to the interactions at the GaAs/graphene interface.

References

1.      Marthinsen, A first-principles Study of epitaxial Interfaces between Graphene and GaAs, MSC Thesis, NTNU, 2014.

2.      A. M. Munshi, D. L. Dheeraj, V. T. Fauske, D.C. Kim, A. T. J. van Helvoort, B.-O. Fimland and H. Weman. Vertically Aligned GaAs Nanowires on Graphite and Few-Layer Graphene: Generic Model and Epitaxial Growth, Nano Let., 12(9):4570–4576, 2012.

PU3

Local and average structure of BiFeo₃ solid solutions

Bo Jiang and Sverre M. Selbach

Department of Materials Science and Engineering, NTNU.

BiFeO₃ is the most studied multiferroic material and is unique in terms of bein the only known room temperature multiferroic compound. BiFeO₃ based solid solutions are also promising lead-free piezoelectric materials. Here the structural distortions caused by substituting Fe with Mn and Bi with La is investigated by synchrotron X-ray diffraction and density functional theory (DFT) calculations. Conventional reciprocal space diffraction data is analyzed by Rietveld refinement and total scattering data analyzed in real space with the pair distribution function (PDF) method. The influence of symmetry conserving and symmetry breaking local distortions caused by doping is discussed with respect to both the limitations of different diffraction methods and physical properties calculated by DFT. The validity of the space group concept for solid solutions is discussed. The ferroelectric polarization is calculated by the Berry phase method and the piezoelectric coefficients from density functional perturbation theory.

PU4

Metal supported proton ceramic electrolyser cells (PCEC) for renewable hydrogen production

Elena Stefan¹, Marit Stange², Christelle Denonville², Runar Dahl-Hansen², Yngve Larring², Per Martin Rørvik², Marie-Laure Fontaine², Reidar Haugsrud¹ and Truls Norby¹

¹ University of Oslo

² SINTEF

Proton ceramic electrolyser cells (PCEC) (Figure 1) have potentially considerable advantages over other types of electrolysers (e.g. solid oxide electrolyser cells - SOEC). They produce dry hydrogen on the cathode side, and the relatively low activation energy of proton conduction enables decrease in operating temperature and thereby utilization of less expensive materials such as steel based interconnects and metal supported electrodes.¹ The lower operating temperature of PCEC also provides the opportunity to use several low to intermediate heat sources as compared to SOECs including heat and steam supplied by geothermal and solar sources, waste from industrial plants etc.

SINTEF and UiO are developing metal supported PCECs (MS-PCEC), where the thick ceramic support layer is replaced with a porous metal support with high mechanical strength. This poster will focus on fabrication and electrochemical characterization of conventional electrolyte and thin (~3 micron), dense electrolyte films using pulsed laser deposition (PLD) onto the alloy/electrode substrates. Further development of the metal supports and optimization of their microstructure as substrates for electrodes obtained by PLD will also be discussed.

References

1.      EFFIPRO – EFFIcient and robust fuel cell with novel ceramic PROton conducting electrolyte,EUFP7 project 2009-2012.

PU5

IN SITU CHARACTERIZATION OF HYDROTHERMAL SYNTHESIS OF PIEZOELECTRIC OXIDES

Susanne Linn Skjærvø, Tor Grande and Mari-Ann Einarsrud

Department of Materials Science and Engineering,Norwegian University of Science and Technology (NTNU)
susanne.l.skjarvo@ntnu.no

References

1. 1D oxide nanostructures from chemical solutions, M.-A. Einarsrud and T. Grande, Chem. Soc. Rev., 2014, 43, 2187-2199. Tutorial review.
2. One-dimensional nanostructures of ferroelectric perovskites, P.M. Rørvik, T. Grande, and M.-A. Einarsrud, Adv. Mater., 2011, 23, 4007-4034. Review
3. Hydrothermal synthesis and characterization of KNbO3 nanorods, G. Z. Wang, S.M. Selbach, Y. D. Yu, X. Zhang, T. Grande, and M.-A. Einarsrud, CrystEngComm, 2009, 11, 1958-63. 
4. Self-assembled growth of PbTiO3 nanoparticles into microspheres and bur-like structures, G. Wang, R. Sæterli, P. M. Rørvik, A. T. J. van Helvoort, R. Holmestad, T. Grande and M.-A. Einarsrud, Chem. Mater., 2007, 19, 2213-2221. 
5. Hierarchical PbTiO3 nanostructures grown on SrTiO3 substrates, P.-M. Rørvik, T. Grande and M.-A. Einarsrud, J. Crystal Growth Design, 2009, 9, 1979-1984.
   

PU6

Perovskite to post-perovskite transition in NaFeF₃

Fabian L.M. Bernal¹, Kirill V. Yusenko¹, Jonas Sottmann¹, Christina Drathen², Jérémy Guignard², Ole-Martin Løvvik³, Wilson A. Crichton² and Serena Margadonna¹*

¹Chemistry Department and Centre for Material Science and Nanotechnology, University of Oslo, Norway
²European Synchrotron Radiation Facility, Grenoble 38043, France
³Department of Physics, University of Oslo, NO-0315 Oslo, Norway

Structural characterizations of the perovskite (Pv) NaFeF₃ and its post-perovskite (pPv) phase (CaIrO₃-type) were studied by performing in situ synchrotron X-ray diffraction and high-temperature high-pressure experiments using multianvil press.  The pPv phases were finally recovered and further magnetic and characterization was performed on both. Ab-initio DFT electronic calculations  at the GGA+U level describe both phases as Mott-Hubbard insulators with magnetic ground states for Pv-NaFeF3 being G-type antiferromagnetic and two-fold degenerate pPv-NaFeF₃  C’- and C”-type antiferromagnets respectively. The onset of the perovskite-to-postperovskite phase transition was reached around 10-15.5 GPa with pPv-NaFeF₃ phase recovered to room temperature.  Strong anisotropic axial compressibilities on pPv NaFeF₃ resulted in lower stabilization pressures and fast increase in the tilting angle ( ϕ₀ = 17.6^o ) compared to the other reported members of ternary post-fluoroperovskites.

Figure

PU7

The Effect of hybrid nanoparticle additives on barrier and mechanical properties of polymer blends as self-healing materials

¹ Huaitian Bu , ¹Juan Yang,  ¹Britt Sommer, ¹Christian Simon, ¹Ferdinand Männle,²Sutima Chatrabhuti and ²Jean-Marie Raquez

¹Materials and Nanotechnology Sector, SINTEF materials and Chemistry, Forskingsveien 1, 0314, Oslo, Norway
²Laboratory of Polymeric and Composite Materials (LPCM), Center of Innovation and Research in Materials and Polymers (CIRMAP), University of Mons, Place du Parc 23, B-7000 Mons, Belgium

Self healing materials, inspired from biological systems, have been attracting increasing research interests since the pilot's work by White in 2001 (White, 2001). These promising materials showed potential applications even in human's daily life, repairing cracks in clothes, coatings for automotive and aerospace, buildings, roads and etc., offering new technology towards long-lasting, safety and cost effectiveness.

Capsule based healing systems are one of the most common-used healing materials, where healing agents are encapsulated/protected by a polymeric/inorganic shell and released either by external stimuli (temperature, pH, etc) or by mechanical forces.  The polymeric capsules should be able to protect the healing agent for a long time, and release the healing agent when cracking in a matrix material occurs. At the same time, the capsules should not influence the workability of the matrix.

In the present work, hydrophobically modified polyhedral oligomeric silsesquioxane (POSS) are used as additive to improve the barrier properties against oxygen and water vapour and impact strength and static mechanical properties of polymer blends. These polymer blends will be applied as capsule shells. Three commonly used polymer materials, PLA, PS and PMMA were blended with different amount of hybrid nanoparticle additives. The results show that modified POSS nanoparticles improve the impact strength of PS blends from 0.5% content. At 5%, toughness drastically increased. Oxygen transmission rate (OTR) will be measured to test the oxygen barrier properties of polymer blends.

References

1.      S. R. White, N. R. Sottos, P. H. Geubelle, J. S. Moore, M. R. Kessler, S. R. Sriram, E. N. Brown & S. Viswanathan, Autonomic healing of polymer composites, Nature 409, 794-797 (2001)

PU8

In operando Structural Investigation oF Na⁺ Intercalation into the Prussian Blue Analogue Na_1.35Mn[Fe(CN)₆]_0.83 · z H₂O

^aJ. Sottmann, ^aF. L. M. Bernal, ^aK.V. Yusenko, ^bH. Emerich and ^aS. Margadonna
^a Chemistry Department and Centre for Material Science and Nanotechnology, University of Oslo, Norway
^b Swiss Norwegian Beamlines, European Synchrotron Radiation Facility, Grenoble, France

Energy storage will play a pivotal role in the rising implementation of intermittent renewable energy sources to the electrical grid. The rechargeable battery technology offers good opportunities to balance electricity supply and demand. Unlike Li, Na is relatively cheap and readily available worldwide. It follows, that there is a huge incentive to develop rechargeable, low-cost sodium ion batteries (SIBs) of reasonable energy density with high dis/charge rate and long service life time¹.

The fundamental understanding of de/intercalation processes (single phase vs. two-phase), structural stability and voltage-composition profiles is pivotal for optimization of electrode materials. For this reason we developed a fully operational set-up (electrochemical cells, sample changer and interfacing software) for in operando quasi-simultaneous X-ray diffraction (XRD) and X-ray absorption spectroscopy (XANES, EXAFS) studies in transmission geometry at the European Synchrotron Radiation Facility (ESRF) on BM01B (Swiss Norwegian Beamlines, SNBL).

Taking advantage of the newly developed equipment, we investigated the prussian blue analogue (PBA) Na_xMn[Fe(CN)₆]_y · z H₂O as a promising low cost, high rate and high capacity cathode material for SIB technology². PBA of formula Na_xMn[Fe(CN)₆]_y can be stabilized in both cubic (Fm-3m) and rhombohedral (R-3m) ordering scheme depending on the amount of guest species. In both structures the Mn^2+/3+ and Fe^2+/3+ reside on alternate corners of a cube of corner-shared octahedra linked by linear (C≡N)^- bridges (Fig. 1(c)). The rhombohedral distortion is due to a cooperative Na⁺ displacement toward the more negative octahedral complex along a cubic [111] axis^2-3.

We have characterized electrochemically and structurally both cubic and rhombohedral initial modifications of Na_1.35Mn[Fe(CN)₆]_0.83 · z H₂O (z = 2.2 and 3.0, respectively). We have observed a series of structural phase transitions which can be clearly linked to the galvanostatic charge/discharge profiles and are further supported by XANES data. The influence of the water content and structural changes will be discussed.

References

1.      M.D. Slater, D. Kim, E. Lee, C.S. Johnson, Adv. Functional Materials (2013), 23, 947.

2.      L. Wang, Y. Lu, J. Liu, M. Xu, J. Cheng, D. Zhang, J.B. Goodenough, Angew. Chem. Int. Ed. (2013), 52, 1964.

3.      Y. Moritomo, T. Matsuda, Y. Kurihara, J. Kim, J. Phys. Soc. Jpn., 2011, 80, 074608.

PU9

Ceramic Composites of Mixed Ionic-Electronic Conductors as Hydrogen Membranes

¹Jonathan. M. Polfus, Wen Xing, Marie-Laure Fontaine, Christelle Denonville, Partow P. Henriksen, Rune Bredesen

¹SINTEF Materials and Chemistry, Sector for Sustainable Energy Technology, Department of Thin Film and Membrane Technology, Forskningsveien 1, NO-0314 Oslo, Norway

Some compositions of ceramic hydrogen permeable membranes are promising for integration in high temperature processes such as steam methane reforming due to their high chemical stability in large chemical gradients and CO₂ containing atmospheres. In the present work, we investigate the hydrogen permeability of densely sintered ceramic composites of two mixed ionic-electronic conductors in various composite ratios: La₂₇W_3.5Mo_1.5O_55.5-δ (LWM) mixed with 30, 40 and 50 wt% La_0.87Sr_0.13CrO_3-δ (LSC) - this composite system for hydrogen membranes has been developed by Universidad Politécnica de Valencia (Spain) and Protia AS (Norway).[1]. Hydrogen permeation was characterized as a function of temperature, feed side hydrogen partial pressure (0.1-0.9 bar) with wet and dry sweep gas (2.5% H2O). In order to assess potentially limiting surface kinetics, measurements were also carried out after applying a catalytic Pt-coating to the feed and sweep side surfaces.

The apparent hydrogen permeability, with contribution from both H₂ permeation and water splitting on the sweep side, was found to be higher for the composites than for the individual materials. The transport properties are discussed and interpreted in terms of each materials ionic and electronic contribution to ambipolar conductivity. Out of the investigated composites ratios, one exhibited the highest apparent H₂ permeability at all temperatures and hydrogen partial pressures for both wet and dry sweep gas. Pt-coating further enhanced the apparent H₂ permeability, particularly at lower temperatures, which indicates that the H₂ permeation is limited by surface kinetics. The apparent H₂ permeability at 700 °C in wet 50% H₂ was 1.1×10^-3 ml min^-1 cm^-1 with wet sweep gas. The present work supports ceramic composites of mixed ionic-electronic conductors as a promising strategy for enhancing the ambipolar conductivity and gas permeability of dense ceramic membranes.

References

1.      J. M. Serra and S. Escolástico, International (PCT) Patent Application No. PCT/EP2014/060708, Applicant: Protia AS (NO).

PU10

Enhancing the O₂ permeability of CaTi_0.85Fe_0.15O₃ based membranes by Mn-doping

¹Jonathan. M. Polfus, Wen Xing, Paul Inge Dahl, Yngve Larring, Marie-Laure Fontaine, Partow P. Henriksen, Rune Bredesen
¹SINTEF Materials and Chemistry, Sector for Sustainable Energy Technology, Forskningsveien 1, NO-0314 Oslo, Norway

CaTiO₃-based perovskite oxides have attracted considerable attention as oxygen permeable membranes in particular due to their chemical and mechanical stability under oxyfuel operating conditions involving high temperature, oxygen chemical potential gradients and CO₂ containing atmospheres. These properties are crucial for the durability and applicability of oxygen permeable membranes and represent the shortcomings of La_0.5Sr_0.5CoO_3-δ and related Co-containing materials despite their significantly higher oxygen flux rates. The O₂ permeability of Fe-doped CaTi_1-yFe_yO_3-δ is found to be highest for y≈0.2: while the total conductivity increases with y, the ionic conductivity decreases above y≈0.2 due to partial ordering of oxygen vacancies.

In order to further improve the ambipolar conductivity and O₂ permeability of CaTi_1-yFe_yO_3-δ membranes, we investigate the effect of  Mn-doping within the composition range CaTi_0.85-xFe_0.15Mn_xO_3-δ (0≤x≤0.4). The O₂ permeability is characterized as function of temperature and feed side p(O₂). As shown in Figure 1, the O₂ permeability increases significantly with Mn-content up to x=0.25 at all temperatures and p(O₂). The permeation results are discussed in terms of structure from in situ synchrotron XRD and density functional theory calculation of the preferred defect charge states and electronic structure.

PU11

Novel precursors for silicon containing materials

¹Karina B. Klepper, ²Frank Herklotz, ¹Helmer Fjellvåg, ¹Ola Nilsen

¹University of Oslo, Department of Chemistry, Centre for Materials Science and Nanotechnology, P.O. Box 1033 Blindern, N-0315 Oslo, Norway (k.b.klepper@kjemi.uio.no)
²University of Oslo, Centre for Materials Science and Nanotechnology, P.O. Box 1048 Blindern, N-0316 Oslo, Norway

We have investigated the suitability of a selection of silicon containing precursors for use in ALD processes. The precursors are bis(dimethylamino)dimethylsilane (BDMADMS), 2,2-disilyltrisilane, 1,2-diisopropyldisilane and hexaethyldisilane. Previously, considerable focus has been given to precursors such as SiCl₄ and SiH₄ and any intermediates of these in combination with O₃, H₂O, H₂O + catalyst or by aid of a plasma source. Si₂Cl₆ has also received notable attention in combination with the above mentioned reactants. Materials deposited with these types of precursors often suffer from high chlorine or -OH contents, and therefore require subsequent high temperature treatments.

We present a new, low temperature thermal ALD process for growth of SiO_x, without the need for a plasma source or an additional catalyst. BDMADBS in combination with ozone resulted in ALD type growth of SiO_x in the temperature range of 125 – 162 °C, with a growth rate of 0.09 nm/cycle. The films were investigated by Fourier transform infrared spectroscopy, X-ray diffraction, atomic force microscopy and electrical measurements.

Fig. 1: Growth rate as function of deposition temperature for the BDMADMS – ozone system.

(OBS: Det er feil i denne figuren. Korrigeres i trykt utgave)

PU12

Computational study of molybdenum trioxide as an intermediate band material

¹Katherine Inzani, Fride Vullum-Bruer, Sverre Magnus Selbach, Tor Grande

¹Department of Materials Science and Engineering, Norwegian University of Science and Technology

In a solar cell a material with an intermediate band between the conduction and valence bands facilitates the absorption of two below band-gap photons, increasing the maximum theoretical efficiency to 63% from 40% for a conventional cell.¹ In this work, the formation of an intermediate band in molybdenum trioxide with sub-stoichiometry is investigated by use of density functional theory. Van der Waals exchange correlation functionals are tested to find which most accurately models the unique layered structure of MoO₃. It is shown that oxygen reduction shifts Mo 4d states from the empty conduction band into the band gap and provides electrons to occupy these states.  Electronic structures with resulting gap states are calculated with respect to the position and concentration of oxygen vacancies. Supercells are constructed depicting ordering of vacancies into the crystallographic shear planes seen experimentally at very low oxygen vacancy concentrations.²

1. Luque, A. & Marti, A. Increasing the efficiency of ideal solar cells by photon induced transitions at intermediate levels. Phys Rev Lett 78, 5014-5017, doi:DOI 10.1103/PhysRevLett.78.5014 (1997).
2. Gai-Boyes, P. L. Defects in Oxide Catalysts: Fundamental Studies of Catalysis in Action. Catalysis Reviews 34, 1-54, doi:10.1080/01614949208021918 (1992).
3. Klimeš, J., Bowler, D. R. & Michaelides, A. Van der Waals density functionals applied to solids. Physical Review B 83, 195131 (2011).

PU13

Surprising Rapid Intercalation Pseudocapacitance Effects in Amorphous LiFePO₄

¹Knut Bjarne Gandrud, ¹Ola Nilsen, ¹Helmer Fjellvåg

¹Centre for Materials Science and Nanotechnology, Department of Chemistry, University of Oslo

Today, well-ordered materials are dominating the field of cathode materials in rechargeable lithium batteries.^[1] Among these crystalline materials, LiFePO₄ is a well-known and widely used cathode material. We have discovered record breaking electrochemical properties of amorphous LiFePO₄ behaving in a pseudocapacitive manner. Through investigation of its thickness dependent electrochemical properties ultrafast charge and discharge rates with minimal capacity loss displaying specific powers above 1 MW/kg LiFePO₄ have been proven. In addition, a self-enhancing kinetic effect is observed during cycling, enabling more than 10 000 cycles at current rates comparable to those found in supercapacitors (11 s charge/discharge). The current findings show that disordered materials can exhibit extremely facile kinetics, which previously was believed to be exclusive to ordered materials.^[2]

References

1.      J. Lee, A. Urban, X. Li, D. Su, G. Hautier and G. Ceder, Science 2014, 343, 519-522.

2.      a) V. Augustyn, J. Come, M. A. Lowe, J. W. Kim, P. L. Taberna, S. H. Tolbert, H. D. Abruna, P. Simon and B. Dunn, Nature Materials 2013, 12, 518-522; b) P. Simon, Y. Gogotsi and B. Dunn, Science 2014, 343, 1210-1211.

PU14

The structural reason for hydrogen capacity loss in Fe-containing bcc alloys – a pdf study

¹Magnus H. Sørby, ¹Henrik Mauroy, ¹Bjørn C. Hauback

¹Institute for Energy Technology, Physics Department, Kjeller, Norway

Hydrogen-absorbing alloys provide a compact and safe way to store hydrogen. Body-centered cubic (bcc) alloys with compositions Ti-V-M (M = Cr, Mn, Fe, Co or Ni) have decent hydrogen capacities (2-3 wt.%) as well as suitable thermodynamics and kinetics for hydrogen storage purposes [1]. Vanadium costs about 300 Euro/kg, about 10 times more than most other first row transition metals, which is a severe limitation for utilization of Ti-V-M bcc alloys for hydrogen storage. A possible workaround is to utilize much cheaper ferrovanadium alloys (FeV = Fe~_0.2V~_0.8) instead (about 30 Euro/kg). The reduction in price comes at the cost of lower hydrogen capacity [2-3].

The structure of bcc alloys and their hydrides are highly disorder with all metal atoms distributed over the same crystallographic site. This makes it challenging to understand structure-property relations by regular powder diffraction or computational methods alone. Still, such relations are crucial to understand in order to intelligently improve the properties of these alloys.

The pair distribution function (PDF) obtained from total scattering experiments contains information about short-range atomic order [4-5]. Total neutron scattering has been performed at ISIS (UK) on a Ti-V-Fe hydride. Reverse Monte Carlo analysis of the data, shows that the material has striking short-ranged features in the atomic arrangement which nicely explains why iron reduces the hydrogen capacity.

References

1.      A.J. Maeland, G.G. Libowitz, J.F. Lynch, J. Less-Com. Met. 104 (1984) 361.

2.      H. Miyamura, T. Sakai, N. Kuriyama, H. Tanaka, I. Uehara, H. Ishikawa, J. Alloys Comp. 253 (1997) 232.

3.      S.F. Santos, J. Huot, J. Alloys Comp. 480 (2009) 5

4.      R.L. McGreevy, L. Pusztai, Molecular Simulation 1 (1988) 359.

5.      M.H. Sørby, Zeitschrift für kristallographie 223 (2008) 617.

PU15

Self heating of ION conducting membranes

¹Marie-Laure Fontaine, Partow. P. Henriksen¹, Rune Bredesen¹,

Thorbjørn Vidvei Larsen², Zuoan Li ² and Truls Norby²

¹SINTEF Materials and Chemistry, Thin Film and Membrane Technology, POB 124 Blindern NO-0314 Oslo Norway

²Department of Chemistry, University of Oslo, Centre for Materials Science and Nanotechnology, FERMiO, Gaustadalleen 21, NO-0349 Oslo, Norway

Self-heating of ceramic membranes is investigated as a means to reduce energy consumption for implementation of membrane technology. Tubular asymmetric La₂NiO_4+d and La_0,87Sr_0,13CrO_3-d membranes were produced with length from 10 to 20 cm (fig.1). A new electrical base for the Probostat^TM cell was designed and built enabling electrical internal heating by the membrane itself using Joule effect when the current passed through the tube. Electrodes were selected among a series of Ag paste, wire, glue, cement and metal particles. The membranes were mounted using nickel plated brass sockets and alumina rings with commercial cement, which were placed in the customized ProboStat^TM cell with 2 internal type K thermocouples. The cell can withstand up to 30 Ampere with 2 power connections at 15 A each. Two power sources were utilized. To simulate a partially heated environment, an external heating mantle was placed outside the quartz tube to raise the baseline temperature. Temperatures up to 960 °C were reached with the short membranes at 13 A and i.e. an effect of ca.250 W. The membranes showed a great stability under electrical heating around 800 °C, close to practical temperatures for gas separation.

Simulation of electrical heating was made in Comsol software. Various physical models including Joule heating and heat transfer in solids and fluids were coupled. Geometrical values were entered according to the membranes and experimental set-up, and various constants for thermal conductivity, heat transfer coefficients etc. were used to give roughly equal temperature fields as experimentally achieved with similar current. A good agreement was found between this simulation work and the experimental results, enabling to further propose improved design of the ceramic membranes, as will be discussed in this presentation. 

Fig. 1: Pictures of membranes.

PU16

A Study of pt-electrode interfaces on nb doped TiO₂ by Cyclic Voltammetry and impedance spectroScopy

Marit Norderhaug and Truls Norby

Department of Chemistry, University of Oslo

Resistance switching is observed in various metal/oxide/metal systems, and is studied for application in resistance random access memories, but the dependence on defects in the oxide and carrier injections through the electrode/film interface are not fully understood[1]. TiO₂ films with Pt electrodes with a high resistance schottky contact shows both bipolar and unipolar resistive switching[1]. The schottky barrier is expected to form due to the differences in work functions, however, the interface might also be ohmic after treatment in oxygen at higher temperatures, which is attributed to lowering of the barrier by diffusion of Pt into TiO₂ at T>1070 K[2]. In the present work, a 1% Nb doped TiO₂ bar sample is characterized with 2, 3 and 4 point voltammetry and impedance spectroscopy in controlled atmosphere and at a range of temperatures, in order to study the defect transport near the interface. Cyclic voltammograms of the sample shows the formation of schottky barriers over both electrodes, which limits the total current in 2-point measurements.

References

1.      Kim, W; Rhee, S, Effect of the top electrode material on the resistive switching of TiO₂ thin film, Microelectronic Engineering, 2010, 87, 98-103

2.      Kirner, U.K.; Schierbaum, K.D.; Göpel, W., Interface-reactions of Pt/TiO₂: Comparative electrical, XPS-, and AES-depth profile investigations, Fresenius' Journal of Analytical Chemistry, 1991,341, 416-420

PU17

Nano-layered Silicon from Calcium disilicide by the use of Ammonium Chlorid Or Hydrogen chloride for the utilization As Anode in Lithium-ion-Batteries

¹²Matthias Herrmann, ¹Frank Krumeich, ¹²Reinhard Nesper

¹ETH Zurich & ²University of Oslo
¹Vladimir Prelog Weg 1, CH-8093 Zürich
²Blindern, N-0315 Oslo

Preparation of nano sized silicon for the utilization in electronic devices, like batteries, gained a lot of interest during the last years [1, 2]. It has been long known that CaSi₂ can undergo topochemical Ca deintercalation, as exhibited by the famous Wöhler and Kautsky siloxene processes [3, 4] which were thoroughly reinvestigated by Hönle et al. [5]. We employed similar simple methods to produce nano-layered silicon from the low price precursor calcium disilicide. As further reactant we applied ammonium chloride or gaseous hydrogen chloride, originating from the dropwise addition of sulphuric acid to sodium chloride. The reaction is exothermic and performs well above 190 °C. The resultant solid products are silicon and calcium chloride. The calcium chloride can be removed by washing with selected solvents. The remaining silicon shows stacked patches of about 20-50 nm thick layers. The performance as anode in lithium-ion-batteries of this easily and cost efficient prepared nano-layered silicon was investigated. For the initial charge, capacities over 800 mAh/mg were observed. However, capacity retention as it is known for many other silicon anodes [1] must be improved.

References

1.      U. Kasavajjula et al., J. Power Sources 163 (2007) 1003–1039

2.      H. Okamoto et al., J. Am. Chem. Soc. 132 (2010) 2717

3.      F. Wöhler. Justus Liebigs Ann. Chem., 127 (1863) 257.

4.      H. Kautsky, G. Blinoff Z. Phys. Chem., 139 (1928) 497

5.      W. Hönle, et al. Phys. Rev. B, 56 (1997) 13132

PU18

Luminescent Properties of Europium Titanium Phosphate Thin Films Deposited by Atomic Layer Deposition

Michael Getz*, Per-Anders Hansen, Helmer Fjellvåg  and Ola Nilsen

Department of Chemistry, University of Oslo, Norway

*E-mail: michael.getz@fys.uio.no

Luminescent thin films containing controlled compositions of europium, titanium, phosphorous and oxygen (Eu_xTi_yP_zO_u) have been deposited by atomic layer deposition, using  Eu(thd)₃ (thd = 2,2,6,6-tetramethyl-3,5-heptanedione) and O₃ for deposition of Eu-O layers, TiCl₄ and H₂O for the Ti-O layers and Me₃PO₄, H₂O  and O₃ for the P-O layers, at a deposition temperature of 300 ˚C. The structure, roughness, thickness and composition have been studied by X-ray diffraction, atomic force microscopy, ellipsometry, and X-ray fluorescence respectively. The optical properties have been characterized with photoluminescence and the extinction coefficient was determined from ellipsometry. The films exhibit the characteristic visible red luminescence of Eu³⁺, though as deposited samples display a high degree of photobleaching when subjected to a 325 nm laser, particularly samples with low Eu-content. Annealing the samples at above 500 ˚C, increases both the photostability and the luminescence of all compositions dramatically and the sample with 8.3 cation % Eu, when annealed at 600˚C, demonstrates the strongest luminescence and photostability. The luminescence is quenched after annealing at 800 ˚C, which, XRD, PL and field emission scanning electron microscopy indicate is due to phase separation.

Left Figure: The luminescence intensity plotted against the composition and annealing temperature for samples annealed at temperatures between 300-800 ˚C.

Right Figure: Normalized PL intensity vs. laser exposure time for a selection of as deposited samples, showing the photostability of the various compositions.

PU19

Electrical Properties of nonstoichiometric Ba_1+xZr_0.85Y_0.15O_2.925 ceramics prepared by solid state reactive sintering

¹Nahum Masó, ²Jonathan M. Polfus, ²Marie-Laure Fontaine and ¹Truls Norby

¹Department of Chemistry, University of Oslo, Centre for Materials Science and Nanotechnology, FERMiO, Gaustadalléen 21, NO-0349 Oslo, Norway
²SINTEF Materials and Chemistry, Sector for Sustainable Energy Technology, Forskningsveien 1, NO-0314 Oslo, Norway

Yttrium-doped barium zirconate, BaZr_1‒xY_xO_3-x/2, shows high-temperature proton conductivity in water-vapor containing atmospheres. It has high chemical and mechanical stability, which allows application in fuel cells, gas sensors, and membrane technology [1,2]. However, to obtain dense ceramics by solid state reaction and conventional sintering, high sintering temperatures (∼1700 °C) are required which leads to barium loss during sintering.

Recently, the solid state reactive sintering method has been applied to fabricate dense BaZr_1‒xY_xO_3-x/2 ceramics at relatively low sintering temperatures, e.g. 1500 oC, using NiO as sintering aid [3]. However, it is observed experimentally (but rarely commented in the literature) that, during sintering, barium (and nickel) loss also occurs by solid state reactive sintering. 

Here we report the effect of barium deficiency/excess on the electrical properties of Ba_1+xZr_0.85Y_0.15O_2.925 (‒0.06 ≤ x ≤ 0.06) ceramics prepared by solid state reactive sintering using 1 wt% NiO as sintering aid.

Acknolegments

We thank the Research Council of Norway (RCN) for financial support through Nano 2021 program (BioPCFC, 219731/O70).

References

1.      K.D. Kreuer, “Proton-conducting oxides”, Annu. Rev. Mater. Res., 2003, 33, 333–359.

2.      H. Iwahara, Y. Asakura, K. Katahira, M. Tanaka, “Prospect of hydrogen technology using proton-conducting ceramics”, Solid State Ionics, 2004, 168, 299–310.

3.      J. Tong, D. Clark, M. Hoban, R. O'Hayre, “Cost-effective solid-state reactive sintering method for high conductivity proton conducting yttrium-doped barium zirconium ceramics”, Solid State Ionics, 2010, 181, 496–503.

PU20

Electrical Properties of undoped and acceptor-Doped (LaO)₂SO₄ Ceramics

¹Nahum Masó, ²Jonathan M. Polfus, ²Marie-Laure Fontaine and ¹Truls Norby

¹Department of Chemistry, University of Oslo, Centre for Materials Science and Nanotechnology, FERMiO, Gaustadalléen 21, NO-0349 Oslo, Norway

²SINTEF Materials and Chemistry, Sector for Sustainable Energy Technology, Forskningsveien 1, NO-0314 Oslo, Norway

Here we report the electrical properties of undoped and acceptor-doped lanthanum oxysulfate (LaO)₂SO₄. Undoped (LaO)₂SO₄ appears to exhibit modest levels of oxide ion conduction when measured in an atmosphere of dry air. On exposure of this sample to moisture, the conductivity decreases approximately half order of magnitude compared to that under dry air conditions. Little effect is observed of doping (LaO)₂SO₄ with Ca or Ba nominally substituting La, indicating that the solid solution range is rather small compared to concentration of native deffects.

Acknolegments

We thank the Research Council of Norway (RCN) for financial support through Nano2021 program (BioPCFC, 219731/O70).

PU21

Crystallisation and electrochemical investigation of α- and β-MoO₃ thin films deposited by Atomic Layer Deposition (ALD)

¹Øystein S. Fjellvåg, Amund Ruud, H. Sønsteby, O. Nilsen, H. Fjellvåg

¹Centre for Materials Science and Nanotechnology (SMN), Department of
Chemistry, University of Oslo, P.O. Box 1033 Blindern, N-0315 Oslo, Norway

Molybdenum trioxide is a promising cathode material for high energy lithium ion batteries. Bulk MoO₃ has a specific capacity close to 300 mAh g^-1 [1], significantly higher than present state-of-the-art batteries eg. LiCoO₂ (~140 mAh g^-1) and LiFePO₄ (~170 mAh g^-1) [2, 3]. Unfortunately, MoO₃ suffers from unknown degradation mechanisms which are yet to be understood. The present work presents an approach for synthesis of model materials in order to gain insight into the electrochemical properties and its degradation mechanism.

Thin films of amorphous MoO₃ have been deposited by ALD at 180 °C using the pulsing sequence [Mo(CO)₆ + (O₃ + H₂O)] [4]. We have thereafter investigated the crystallisation process in order to gain control over formation of the orthorhombic α-phase and the meta‑stable monoclinic β-phase.

As deposited, the MoO₃ thin films were amorphous. Pristine films of α-MoO₃ were successfully synthesized by heat treatment at 500 °C for 10 minutes by rapid thermal processing. It was more challenging to synthesize phase pure films of the meta-stable β-MoO₃ phase. However, through an in situ X-ray diffraction study of the crystallization process, we observed that the β-MoO₃ phase was formed at 230 °C, much lower than what previously reported (500 °C) [4]. Phase pure films of β-MoO₃ were obtained by annealing at 235 °C for 1 day. Furthermore cyclic voltammetry were performed in order to investigate at which voltage against lithium the redox reactions occurred for the different phases.

References

1.      M.E. Spahr et al. Journal of Power Sources 54 (1995) 346-351.

2.      B. Huang et al. Journal of Applied Electrochemistry 28 (1998) 1365-1369.

3.      L.-X. Yuan et al. Energy & Environmental Science 4 (2011) 269-284.

4.      M. Diskus et al. Journal of Materials Chemistry 21 (2011) 705-710.

PU22

First-principles study of structural stability, dynamical and mechanical properties of Li₂FeSiPO₄ polymorphs

¹P. Vajeeston, H. Fjellvåg

¹Center for Materials Sciences and Nanotechnology, Department of Chemistry, University of Oslo, P.O. Box 1033 Blindern, N-0315 Oslo, Norway

Density functional theory (DFT) provides an extremely valuable tool for predicting structures and energetics of materials for both finite and periodic systems. In the present work the relative stability, electronic structure, thermo dynamical, and mechanical properties of potential cathode material Li₂FeSiO₄ and its polymorphs have been studied by state-of-the-art density-functional calculations. Among the 11 structural arrangements considered for the structural optimization calculations, the experimentally known monoclinic P2₁ modification becomes the ground state structure. Application of pressure makes sequence of phase transitions from P2₁ ® Pmn2₁ ® I222 modification and the estimated transition pressures are 0.38 and 1.93GPa respectively. The electronic structures reveal that all these polymorphs are non-metals with calculated band gap varying between 3.0 to 3.2 eV.   The involved energy difference between the different polymorphs is small and all these polymorphs are dynamically stable. The calculated single crystal elastic constants reveal that all the studied Li₂FeSiO₄ polymorphs are easily compressible and are mechanically stable phases.  

 PU23

Investigation of Li⁺ insertion in columbite structured FeNb₂O₆ and rutile structured CrNb₂O₆ materials

Pushpaka B. Samarasingha, Chris I. Thomas, and Helmer Fjellvåg

Centre for Materials Science and Nanotechnology, University of Oslo, Oslo, Norway. 0371

Materials with the ability to reversibly incorporate lithium are of great technological and scientific importance forming the basis of Li-ion batteries (LIB). There is a constant drive to improve the performance of LIB ^[1] leading to the continual search for new materials, especially for the cathode. Previous studies show that Li⁺ can be inserted in columbite materials,^[2] MNb₂O₆ (M = Mn, Co, Ni, Cu, Zn, Cd, Ca, Mg). Rutile (TiO₂^[3]) and many rutile materials^[4] are also under investigation for use in LIB.

Columbite structured FeNb₂O₆ and rutile structured CrNb₂O₆ materials were synthesized in the form of powders and 2032 coin cells were assembled for electrochemical testing. Reversible Li⁺ insertion of upto 0.47 moles compares well to the known columbites MgNb₂O₆, (0.27) and CaNb₂O₆ (0.26). Galvanostatic charge-discharge curves of the samples show three plateaus representing Li⁺ intercalation steps. The amount of intercalated Li⁺ per formula unit is reduced by more than 50% during the second cycle then Li⁺ de-intercalation values remain steady for 10 cycles. The cyclic voltammograms  show three oxidation/reduction peaks assigned to the red-ox couples; Nb^5+/4+, Nb^4+/3+ and Nb^3+/2+. CrNb₂O₆ also show a fourth peak assigned to the redox couple Cr^3+/2+ meaning the oxidation state arrangement is Cr³⁺Nb⁴⁺Nb⁵⁺O₆.

Fig. 1: Galvanostatic charge-discharge curves of FeNb₂O₆ Inset shows Li⁺ de/intercalation per formula unit

References

1.      R. Wagner, N. Preschitschek, S. Passerini, J. Leker, M. Winter, J. Appl. Electrochem  2013, 43, 481-496.

2.      M. A. Reddy and U. V. Varadaraju, J. Phys. Chem. C 2011, 115, 25121-25124.

3.      K. Kanamura, K. Yuasa and Z. Takehara, J. Power Sources 1987, 20, 127-134.

4.      D. W. Murphy, S. F. J. Di, J. N. Carides and J. V. Waszczak, Mater. Res. Bull. 1978, 13, 1395-1402.

PU24

Characterization of electrodes on ionic conductors with transport of more than one type of charge carriers

¹Ragnar Strandbakke, Truls Norby
¹Department of Chemistry, University of Oslo, FERMiO, Gaustadalléen 21, NO-0349 Oslo, Norway.

The work addresses characterization of electrodes on electrolytes with transport of more than one type of charge carriers, modelled in parallel “rails” where the resistances associated with electrolyte transport, charge exchange at the electrolyte / electrode interface and diffusion / adsorption at the electrode surface are connected in series (figure 1) in each rail. Using electrochemical impedance spectroscopy, deconvoluted electrolyte and electrode resistances are obtained and seen as parallel combinations of the processes undertaken by each individual charge carrier. By expressing these processes with Arrhenius-like equations, the resistances associated with each charge carrier can be parameterized and the total system can be modelled [1].

References

1.      R. Strandbakke, V. Cherepanov., A. Zuev, D. S. Tsvetkov, C. Argirusis, G. Sourkouni-Argirusis, S. Prünte, T. Norby, Gd- and Pr-based double perovskite cobaltites as oxygen side electrodes for proton ceramic fuel cells and electrolyser cells. Submitted to Solid State Ionics, 2014.

The work is funded by the European Union; ERA.Net RUS project #197 - PROTON

PU25

Correlation between bulk and surface kinetics of proton conducting oxides

¹Ragnhild Hancke, Zuoan Li, Reidar Haugsrud

¹Department of Chemistry, University of Oslo, FERMiO, Gaustadalléen 21, NO-0349 Oslo, Norway.

The hydrogen flux through dense, mixed conducting oxides increases when the membrane thickness decreases. However, at a certain point, also the reaction at the gas-solid interface will start to influence the overall H₂ flux, and less can be gained by reducing the proton transport length further. With the optimization of thin film fabrication it is therefore becoming increasingly important to investigate surface reactions and understand the relation between bulk and surface kinetics. 

In the present study we have investigated bulk diffusion and surface exchange (described by D and k, respectively) of the proton conducting oxides BaCe_0.9Y_0.1O_3‑δ (YBC) and La_27.15W_4.85O_55.28v_0.73 (LWO). Transient thermogravimetry and ToF-SIMS profiling have been undertaken to extract both chemical (ΔpH₂O) and tracer (H/D exchange) transport coefficients. We show that a strong correlation between log D and log k applies to YBC and LWO, similar to what has been demonstrated for a range of oxide ion conductors [1]. The activation enthalpies for surface exchange and for bulk diffusion are related by a ratio of approximately 1:2, valid for both chemical and tracer coefficients (Fig. 1). The correlation is different for LWO under reducing conditions at high temperatures which we ascribe to an increased concentration of electronic charge carriers. Under these conditions, the surface exchange process shifts from one predominated by the acid-base reaction with water, to a redox reaction with hydrogen. Isotherms of k are furthermore used as a starting point for an analysis of the elementary surface reaction steps and rds.

Fig. 1: log k – log D plot for chemical (δ) and tracer (*) transport coefficients of YBC and LWO.

References

1.      R.A. De Souza, J.A. Kilner, Solid State Ionics, 126 (1999) 153-161.

PU26

Development Of High-Performance Ceramic Sorbent For High-Temperature CO₂ separation and hydrogen production

¹Saima Sultana Kazi, Johann Mastin

 ¹Institute for Energy Technology (IFE), Kjeller, Norway

Looping cycles for CO₂ capture, employing a CaO-based sorbent represents an important new technology for the efficient separation of CO₂ from combustion/ gasification gases. The process is based on the reversible gas-solid carbonation reaction of CaO at high temperature. The optimal operation window for the exothermic carbonation reaction is 550-650⁰C. The reverse endothermic reaction is favored at high temperature and temperature above 850⁰C is required to regenerate the sorbent at atmospheric pressure and produce an almost pure CO₂ stream. The CaO-looping process shows the advantage to be used in two different high-temperature CO₂-capture technologies:

- Post-combustion CO₂ capture for energy generation and industry processes

- Pre-combustion CO₂ capture for energy generation and/or hydrogen production

The sorbents most commonly considered for high-temperature CO₂ capture are the natural sorbents (limestone and dolomite). However, CO₂ capture capacity of unmodified natural sorbents decreases rapidly with increasing number of looping cycles, mainly due to sintering and pore closure effects. Additionally, the mechanical properties are suboptimal due to particle attrition during long-term operation in a cyclic mode in circulating fluidized bed reactors.

To overcome those problems, extensive efforts were put on the development of synthetic Ca-based sorbents worldwide. Institute for Energy Technology (IFE) has developed a novel solid sorbent for high-temperature CO₂ capture applications. The developed sorbent shows a genuine composite structure made of stable sub-micro particles of CaO (~100nm) homogeneously distributed in a micro-porous mayenite matrix. The controlled size of the nanoparticles and the layered structure of the particles on the surface of the pores of the matrix are believed to improve significantly the chemical stability of the sorbent [1-2].

A critical factor for future industrial applications is to develop a low-cost synthesis method based on cheap raw materials. For this purpose, IFE developed a new hydrothermal synthesis based on low-temperature reaction between calcium and aluminium precursors to form a stable calcium aluminate-based sorbent. Critical synthesis parameters such as nature of the precursors, processing gas conditions as well as calcination temperature strongly affect the sorption kinetics and stability of the final solids. Another important aspect of the sorbent preparation is the development of an efficient agglomeration process by which the synthetic micro-powder is further assembled into particles of suitable size with the desired mechanical and chemical properties for using in fluidized bed reactor systems.

In this project, the reactive synthetic sorbent micro-powder developed at IFE was agglomerated into solid spherical particles using high-shear agglomerator. Crushing strength measurement showed that the developed particles had a significantly improved mechanical properties compared to calcite and dolomite.

In this work, preparation method as well as chemical and mechanical properties of the sorbent particles has been assessed. The influence of various process parameters and agglomeration techniques on mechanical stability of the sorbent particles and their long-term chemical stability during capture/regeneration will be presented.

Fig. 1: Synthetic calcium based CO₂ sorbent granulated using high-shear agglomerator.

References

1.      Mastin, J., Aranda, A. and Meyer, J. New synthesis method for CaO-based synthetic sorbents with enhanced properties for high temperature CO₂-capture, Energia Procedia 4, 2011, 1184–1191.

2.      Mastin J., Meyer J. and Råheim A., Particulate, heterogeneous solid CO₂ absorbent composition, method for its preparation and method for separating CO₂ from process gases with use thereof. Patent Pending.

PU27

Hydrogen permeation and transport properties of bzy and gco composites.

Sarmad W. Saeed

Department of Chemistry, University of Oslo, Centre for Materials Science and Nanotechnology, FERMiO, Gaustadalléen 21, NO-0349 Oslo, Norway

Hydrogen permeation in oxides relies on ambipolar transport of protonic and electronic defects. Many materials with high proton conductivities such as Y-doped barium zirconate (BZY) suffer from low electronic conductivity and thereby show low hydrogen flux. Two-phase composites consisting of a proton conductor and an electronic conductor may overcome this limitation.

In this work we study the hydrogen permeation and electrical properties of a series of composites consisting of BZY and Gd-doped ceria (GCO) as the protonic and electronic conducting phase, respectively. The samples are made by hot-pressing and the measurements are performed as a function of temperature,  gradient and . The H₂ production rate at 1000 °C is  mL min^-1 cm^-1. However the apparent flux seems to be dominated by water splitting and hence transport of oxide ions and electrons.

PU28

Impedance study of Model electrodes for use in carbon containing atmospheres

¹Shay A. Robinson, ²Christian Kjølseth, ¹Truls Norby

¹Department of Chemistry, University of Oslo, FERMiO, Gaustadalleén 21, NO-0349 Oslo, Norway
²Protia AS, Gaustadalleén 21, NO-0349 Oslo, Norway

BaZr_0.7Ce_0.2Y_0.1O_3-δ (BZCY72) protonic ceramic electrochemical devices have been demonstrated to perform well as fuel cells and hydrogen pumps [1-2]. In order to operate in highly reducing and carbonaceous biogas atmospheres, these devices require electrodes characterized by a resistance to coke formation, good electrical conductivity, an extended triple-phase boundary, adequate porosity, and electrolyte compatibility [3-4]. As a basis to compare and contrast multi-phase electrodes that will be developed in the future, it is necessary to identify key thermodynamic and mechanistic effects of each material. 

Cu is known for its high electrical conductivity and resistance to coke formation; however the proton conductivity of the metal is not well defined. In this work, single-phase Cu is compared to Ni and Pt in a point electrode configuration using a BZCY72 pellet with 1 wt.% ZnO added to facilitate densification. Impedance measurements are conducted from 500°C-900°C in steps of 50°C and for pH₂ at 5%, 10% and 20%, in both 2.7% H₂O vapor and dry atmospheres. Preliminary impedance data was deconvoluted with a Randles-like equivalent circuit, with the real-axis intercept regarded as the total electrolyte resistance. Active area was extrapolated by

Figure 1: (A) Nyquist plots for a Cu point electrode on a 1 wt.% ZnO – BZCY72 pellet. (B) Bulk conductivity σ_b and (C) charge transfer R_ct and diffusion R_d resistance vs. inverse temperature

Comparing experimental data to literature values for the bulk conductivities of BZY, BCY and BZCY [5-6]. Polarization resistance was regarded as the sum of the charge transfer resistance (higher frequency) and diffusion resistance (lower frequency). As can be ascertained from Figure 1 C, R_ct is non-linear indicating different activation energies and conductivity regimes limited by proton and oxide ion conductivities at high and low temperatures, respectively. However, diffusion resistance dominates over charge transfer resistance, with a relatively constant activation energy and resistance approximately doubling over the experimental temperature range. At lower temperatures of 600-650 °C , a third intermediate frequency arc was observed in the impedance spectra.

References

1.      H. Iwahara, Solid State Ionics, 86-88, (1996), 9–15.

2.      H. Iwahara, Solid State Ionics, 77, (1995), 289–298.

3.      V. Dusastre, J. A. Kilner, Solid State Ionics, 126, (1999), 163.

4.      S. W. Tao, Q. Y. Wu, D. K. Peng, G. Y. Meng, J. Appl. Electrochem., 30, (2000), 153.

5.      K.D. Kreuer, Annu. Rev. Mater. Res. 33 (2003), 333–359

6.      S. Ricote, N. Bonanos, A. Manerbino, W.G. Coors, Int. Journal of Hydrogen Energy, 37, (2012), 7954-7961

PU29

Modelling of surface conduction of porous oxides

Sindre Østby Stub¹, Per Martin Rørvik², Reidar Haugsrud¹and Truls Norby¹

¹Centre for Materials Science and Nanotechnology, Department of Chemistry, University of Oslo

²SINTEF Materials and Chemistry, Oslo Norway

Increasing conductivity with decreasing temperature in wet atmosphere in nanocrystalline and porous oxides have been reported during last years [1,2]. The origins of these relatively high observed conductivities are still not completely understood.

In this work, we study porous TiO₂ samples fabricated by solid-state reaction and hot-pressing. The microstructure is studied by SEM, BET and XRD. The conductivity is investigated with impedance spectroscopy in wet oxygen below 400 °C. In the figure below, we show increasing conductivity due to increasing water activity in TiO₂.

In order to understand fully the conductivity contributions and mechanisms, we are in the process of developing a model of the conduction in porous oxide samples based on fundamental surface chemistry. By comparing results from impedance spectroscopy with theoretical results from our model, we find that the surface area and surface behaviour plays the key role for the enhancement of the proton transport at low temperatures. The amount of water on the surface seems to be controlled by gas adsorption, and not capillary condensation as often suggested in the literature [2].

Figure 2. Impedance measurements of porous TiO₂ in wet oxygen. Left: bulk conductivity at room temperature; Right: Temperature ramp at 10 kHz at pH₂O = 0,023 atm.

References

1.      Avila-Paredes, H.J., et al., Protonic conductivity of nano-structured yttria-stabilized zirconia: dependence on grain size. Mat Chem, 2010. 20: p. 990

2.      Gregori, G., M. Shirpour, and J. Maier, Proton Conduction in Dense and Porous Nanocrystalline Ceria Thin Films. Adv Func Mat, 2013. 23: p. 5861

PU30

Dual-phase membrane for high temperature CO₂ separation

Wen Xing¹, Thijs Peters¹, Marie-Laure Fontaine¹, Anna Evans², Partow Pakdel Henriksen¹ Truls Norby², Rune Bredesen¹

¹ SINTEF Materials and Chemistry, Thin Film and Membrane Technology, POB 124 Blindern NO-0314 Oslo Norway

² Department of Chemistry, University of Oslo, Centre for Materials Science and Nanotechnology, FERMiO, Gaustadalleen 21, NO-0349 Oslo, Norway

Dual-phase CO₂ separation membranes consisting of a molten carbonate phase and a solid phase made from either an electronically conducting metal or ceramic, or an oxide ion conducting ceramic (mixed conductor or electrolyte type), can provide ambipolar transport of CO₂ and/or O₂ at high temperatures ^[1-5]. Therefore, the dual-phase membranes are the candidates used in CO₂ capture processes and membrane reactors. Though encouraging flux and selectivity results are obtained, there is a need for further investigation of these novel membranes and their transport properties.

In this contribution, the CO₂ flux for CeO₂ supported dual-phase membranes were studied as a function of temperature. The CO₂ flux was found to be dominated by oxide ion transport under dry conditions. The effects of support oxide porosity on CO₂ flux were investigated and the effect of oxide addition to CO₂ flux was examined. Under wet conditions, a significant increase in CO₂ flux was found, which was more significant by introducing steam to sweep side than that to feed side. This effect was explained by the ambipolar transport of CO₃^2- and OH^- which provides another effective route for CO₂ transport and is important for membrane process design in real working conditions. Moreover, the membrane stability was studied under conditions relevant for pre-combustion CO₂ capture showing little degradation for a period of ~1500 h. During this period, the membranes were found to be 100% selective to CO₂.

References

1. J.L. Wade, C. Lee, A.C. West, K.S. Lackner, Composite electrolyte membranes for high temperature CO₂ separation, Journal of Membrane Science, 369 (2011) 20-29.
2. M.L. Fontaine, T.A. Peters, M.T.P. McCann, I. Kumakiri, R. Bredesen, CO₂ removal at high temperature from multi-component gas stream using porous ceramic membranes infiltrated with molten carbonates, Energy Procedia, 37 (2013) 941-951.
3. Z. Rui, M. Anderson, Y. Li, Y.S. Lin, Ionic conducting ceramic and carbonate dual phase membranes for carbon dioxide separation, Journal of Membrane Science, 417 (2012) 174-182.
4. Y. Li, Z. Rui, C. Xia, M. Anderson, Y.S. Lin, Performance of ionic-conducting ceramic/carbonate composite material as solid oxide fuel cell electrolyte and CO₂ permeation membrane, Catalysis Today, 148 (2009) 303-309.
5. M. Anderson, Y.S. Lin, Carbonate–ceramic dual-phase membrane for carbon dioxide separation, Journal of Membrane Science, 357 (2010) 122-129.

PU31

Disordered crystal structure of MoO₃ nanobelts

Wojciech A. Sławiński, Øystein S. Fjellvåg, Amund Ruud, and Helmer Fjellvåg

Centre for Materials Science and Nanotechnology, Department of Chemistry, University of Oslo, PO Box 1033, 0315 Oslo, Norway

One of the most applied power sources today are rechargeable lithium-ion batteries. This is due to its high energy density, high voltage, no memory effect and long cycle life [1]. The most commonly used anode material is graphite. There is now lot of efforts done to discover new materials to improve batteries properties. One interesting candidate is molybdenum trioxide MoO₃, either as anode or cathode material [2]. Its anodic capacity of 1100 mAh/g is well above 372 mAh/g for graphite [3]. However, our focus is rather on MoO₃ as cathode material. Importantly, it has been reported that changing the MoO₃ crystallite size into the nano scale regime significantly improves its electrochemical properties [4-5]. It is therefore essential to gain insight into the crystal structure of material with different particle morphologies at the nanoscale in order to better understand the mechanism behind enhanced electrochemical properties.

We present an extensive study on the disordered structure of MoO₃ nanobelts. Bulk and nanobelt samples of MoO₃ were investigated by synchrotron radiation powder diffraction, supplemented by TEM. The observed diffraction patterns for nanobelt and bulk sample reveal significant differences which cannot be explained just by diffraction line broadening due to limited crystallite size. The MoO₃ structure can be described as consisting of two layers (A and B) stacked alternatingly (ABAB…). In the nanobelts these layers are no longer stacked perfectly (probability of stacking fault determined to 0.42), while the bulk MoO₃ is perfectly ordered in an ABAB... sequence. It is proposed that the stacking faults may influence electrochemical properties of the nanobelts compared to the bulk material. This is reasonable since the stacking faults occur in interlayers being likely candidates for Li-ion intercalation.

References

1.      Scrosati, B. Nature 1995, 373, 557-558.

2.      Wang, X.; Nesper, R.; Villevieille, C.; novak, P. Adv. Energy Mater. 2013, 3, 5, 606-614

3.      Chernova, N.; Roppolo, M.; Dillon, A.; Whittingham, M. Journal of Materials Chemistry 2009, 19, 2526-2552.

4.      Brezesinski, T.; Wang, J.; Tolbert, S.; Dunn, B. Nature Materials 2010, 9, 146-151.

5.      Hashem, A.; Askar, M.; Winter, M.; Albering, J.; Besenhard, J. Ionics 2007, 13, 3-8.

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KM - Kvantekjemi og modellering

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KM1	First Principles Modeling of Solid Acid Catalysis Supported by Experiments: From Kinetics to a Reactivity Descriptor Rasmus Y. Brogaard   (UiO)
KM2	The π→π✴ excitation energy of azo compounds by a combined charge-transfer and point-dipole interaction model Shokouh Haghdani  (NTNU)
KM3	Relativistic four-component calculations of indirect nuclear spin-spin coupling using hybrid functionals Stanislav Komorovsky   (UiT)
KM4	Multi-level coupled cluster theory Kristin Marie Skjelbred  (NTNU)
KM5	Mesoscopic modeling of DNA denaturation rates Oda Dahlen  (NTNU)
KM6	Gluing potential energy surfaces with rare event simulations Anders Lervik
KM7	Molecular excitation energies with a range-separated second-order dynamical Bethe-Salpeter kernel Elisa Rebolini
KM8	Real-time solution of the time-dependent Dirac-Coulomb equation Márius Kádek

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Abstracts

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KM1

First Principles Modeling of Solid Acid Catalysis Supported by Experiments: From Kinetics to a Reactivity Descriptor

Rasmus Y. Brogaarda,c,d,*, Chuan-Ming Wanga,b, Unni Olsbyed,e, Yves Schuurmane, Reynald Henryd, Stian Svelled, Bert M. Weckhuysenf, Jens K. Nørskova,c, Felix Studta,*

a SUNCAT Center for Interface Science and Catalysis, SLAC National Accelerator Laboratory, USA
b Shanghai Research Institute of Petrochemical Technology SINOPEC, China
c Department of Chemical Engineering, Stanford University, USA
d inGAP Centre for Research-based Innovation, University of Oslo, Norway
e IRCELYON, Université Lyon 1-CNRS, France
f Debye Institute for Nanomaterials Science, Utrecht University, The Netherlands

  emails: brogaard@smn.uio.no, studt@slac.stanford.edu


Recent work has reported discovery of metal surface catalysts by employing a descriptor-based approach, establishing a correlation between few well-defined properties of a material and its catalytic activity [1]. This theoretical work introduces a similar approach in solid acid catalysis, focusing on alkene-methanol reactions catalyzed by zeotype solid acid catalysts.

We employed periodic density functional theory (DFT) to model the reactions in the acid catalysts, using the BEEF-vdW functional constructed to describe chemical bonding as well as van der Waals interactions [2]. As a starting point, we derived kinetics of isolated steps in several alkene-methanol reactions in a conventional zeolite using a temporal analysis of products (TAP) reactor. The experimental results quantitatively validate the kinetics derived from transition-state theory and DFT calculations [3].

Using the same computational setup, we then investigated zeotype materials with Brønsted acid strength altered by isomorphic substitution of transition metal atoms in the catalyst framework. We established linear scaling relations between the heat of ammonia adsorption, H(NH3), at acid sites and the energy of intermediates and transition states. ΔH(NH₃) hence captures the interactions that determine the stability of intermediates and transition states, and the scaling relation quantifies the reactivity of the acid site towards a given species. The scaling relations enable micro-kinetic modeling to predict a quantitative relation between the descriptor ΔH(NH3) and the catalytic activity, the rate of alkene methylation [3] (Figure 1). We propose this as a step towards in silico design of solid acid catalysts.

Figure 1. Predicted rate of propene-methanol reaction as a function of calculated heat of ammonia adsorption in zeotype solid acid catalysts.

Acknowledgments

Work supported by the U.S. Department of Energy Chemical Sciences, Geosciences and Biosciences Division under Contract No. DE-AC02-76SF00515 and the Norwegian Research Council under contract No. 174893. C.-M.W. acknowledges financial support from the National Science Foundation of China (21103231).

References

1. F. Studt, F. J. K. Nørskov, et al. Science 320 (2008) 1320.
2. J. Wellendorff, J.K. Nørskov, et al., Phys. Rev. B 85 (2012) 235149.
3. R. Y. Brogaard, U. Olsbye, et al. J. Catal. 314 (2014) 159.
4. C.-M. Wang, F. Studt, et al. J. Phys. Chem. Lett. 5 (2014) 1516.
   

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KM2

THE π→π✴ EXCITATION ENERGY OF AZO COMPOUNDS BY A COMBINED CHARGE-TRANSFER AND POINT-DIPOLE INTERACTION MODEL

Shokouh Haghdani, Nazanin Davari, and Per-Olof Åstrand

Department of Chemistry, Norwegian University of Science and Technology (NTNU), N-7491 Trondheim, Norway

A combined charge-transfer and point-dipole interaction (CT/PDI) model is used to investigate the frequency-dependent polarizability and π→π✴ excitation energy for a set of azobenzene molecules with different functional groups in the para-position. Time-dependent density functional theory (TDDFT) calculations of the complex frequency-dependent polarizability are used to parameterize the model. Comparisons between the results of the CT/PDI model with the TDDFT calculations and experimental data demonstrate that the CT/PDI model is fully able to reproduce the static polarizability as well as the π→π✴ excitation energy. The point-dipole contributions of the nitrogen atoms in the azo bond and the adjacent carbon atoms have the main role for the large polarizability in particular at absorption. Charge-transfer from the functional groups at the end of the molecules to azo group in the middle of the molecule introduces shifts of the position of the π→π✴ excitation energy.

References

1. Smalø, H. S.; Åstrand, P.-O.; Mayer, A. Combined Nonmetallic Electronegativity Equalisation and Point-Dipole Interaction Model for the Frequency-Dependent Polarisability, Mol. Phys. 2013, 111, 1470.
2. Smalø, H. S.; Åstrand, P.-O.; Jensen, L. Nonmetallic Electronegativity Equalization and Point-Dipole Interaction Model Including Exchange Interactions for Molecular Dipole Moments and Polarizabilities, J. Chem. Phys. 2009, 131, 044101.
3. Mayer, A.; Lambin, P.; Åstrand, P.-O. An Electrostatic Interaction Model for Frequency-Dependent Polarizability: Methodology and Applications to Hydrocarbons and Fullerenes, Nanotechnology 2008, 19, 025203.
   

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KM3

Relativistic four-component calculations of indirect nuclear spin-spin coupling using hybrid functionals

Stanislav Komorovsky^a, Michal Repisky^a , Olga L. Malkina^b , Vladimir G. Malkin^b , Kenneth Ruud^a

a Centre for Theoretical and Computational Chemistry, University of Tromsø - The Arctic University of Norway, N-9037 Tromsø, Norway
b Institute of Inorganic Chemistry, Slovak Academy of Sciences, Dúbravská cesta 9, SK-84536 Bratislava, Slovakia

A relativistic four-component method for calculations of indirect nuclear spin-spin coupling tensors at the non-collinear density functional level of theory is reported. The present implementation differs from the previously published one [1, 2] in two main points. 1) no approximations to the four-center integrals and the exchange-correlation functional were made and 2) the contribution from the exact exchange is included thus allowing the use of hybrid DFT functionals. All calculations employ a state-of-the-art four-component approach using a restricted magnetically balanced basis set (mDKS-RMB). Benchmark calculations are presented for the set of small systems as well as chemically relevant systems with more than 50 atoms. Importance of proper treatment of relativistic effects in calculation of indirect nuclear spin-spin coupling constants between one heavy and one light nucleus or between two heavy nuclei is emphasized. For this purpose the results obtained with the new approach are compared with the results of more approximate methods as well as with available experimental data.

References

1. M. Repisky, S. Komorovsky, O. L. Malkina, and V. G. Malkin, Chem. Phys. 356, 236 (2009).
2. A. Křístková, S. Komorovsky, M. Repisky, V. G. Malkin, and O. L. Malkina, “Relativistic Four-Component Calculations of Indirect Nuclear Spin-Spin Couplings with Efficient Evaluation of The Exchange-Correlation Kernel”, in preparation.
   

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KM4

MULTI-LEVEL COUPLED CLUSTER THEORY

Kristin Marie Skjelbred¹, Rolf Heilemann Myhre¹, Henrik Koch¹, Alfredo M. J. Sánchez de Merás²

1 Department of Chemistry, NTNU 7491 Trondheim, Norway
2 Institute of Molecular Science , University of Valencia , Valencia , ES-46071 , Spain


As a part of the ongoing development of the multi level coupled cluster (MLCC) model ECC2, we have included the computation of transition moments associated with certain excitation energies. The ECC2 model divides the system into two subsystems where different levels of theory are used. Specifically coupled cluster singles and doubles (CCSD) is used as the higher level, while the approximate model CC2 is used as the lower level. This allows for retention of computational accuracy while reducing the complexity and consequently the cost of the calculations, assuming the active space has been chosen correctly. The ECC2 model uses Cholesky decomposition [1] for partition-ing of the system, both because it reduces computational complexity and because it lets the user use chemical expertise. Transition moments are a local property and limiting the active space to the orbitals taking part in the corresponding excitation leads to a great reduction in scaling. The ECC2 model is implemented in the Dalton [2] software package, and has proven to give excitation energies comparable to CCSD results [3]. We have implemented different versions of the ECC2 model; both the version with two levels of theory and a version where we have included a third level of theory, namely CCS. The model is under development and currently single point energy can be calcu-lated with up to four levels of theory, CCS, CC2, CCSD and CCSD with non-iterative triples, CCSD(T). The highest level of theory (CC3) has not yet been included for exci-tations energies and transition moments.


References

1. A. M. J. Sánchez de Merás, H. Koch, I.G. Cuesta and L. Boman, J. Chem. Phys. 132:204105 (2010);
2. "The Dalton quantum chemistry program system", WIREs Comput. Mol. Sci. 4:269 (2014);
3. R. H. Myhre, A. M. J. Sánches de Merás and H. Koch, J. Mol. Phys. 111:1109 (2013);
   

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KM5

Mesoscopic modeling of DNA denaturation rates

Oda Dahlen, Titus S. Van Erp

Department of Chemistry, NTNU 7491, Norway

DNA denaturation rate constants were calculated using the mesoscopic Peyrard-Bishop-Dauxois (PBD) model with two different parameter sets. A large amount of sequences were investigated by varying the ratio of weak to strong base pairs, the order of the base pairs in the chain, the length of the chain and the temperature. We found, contrary to a previous study, that an even distribution of the weak and strong bps in the chain does not always result in the largest denaturation rate constant. Further on, we altered the PBD model slightly in order to investigate DNA hairpins. Our work is the first quantitative study in which dynamical data obtained from the PBD model have been compared with experimental data. We found DNA denaturation rates being orders of magnitude larger than experimental ones, implying that significant improvements has to be done to the model in order to produce realistic dynamical data.

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KM6

Gluing potential energy surfaces with rare event simulations

Anders Lervik and Titus S. van Erp

Department of Chemistry, Norwegian University of Science and Technology, Trondheim, Norway

Many processes in nature arise from the spontaneous transition between stable states separated by a activation barrier. If the activation barrier is sufficiently high, the transition can be considered as a rare event and the time-scale for the transition (e.g. milliseconds) can be many orders of magnitude larger than the molecular time-scale (e.g. femtoseconds). This poses a challenge for simulation techniques which aim to accurately model rare events and specialized approaches are needed.

Here, we develop a new method for rare events simulations combining replica exchange transition interface sampling (RETIS)[1] with two different potential energy surfaces. The method can be used as a dynamical version of QM/MM to connect classical dynamics with Ab initio dynamics and thus decrease the computational cost. We describe the method, exemplify it and demonstrate how it can be used to decrease the computational cost of studying rare event transitions.

References

1. van Erp, T. S. Phys. Rev. Lett. 2007, 98, 268301

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KM7

Molecular excitation energies with a range-separated second-order dynamical Bethe-Salpeter kernel

Elisa REBOLINI¹,  Julien TOULOUSE and Andreas SAVIN²

1 Department of Chemistry, and Centre for Theoretical and Computational Chemistry (CTCC), University of Oslo, Norway
2 Sorbonne Universités, UPMC Univ Paris 6, and CNRS, UMR 7616, LCT, F-75005, Paris, France

In the past years, time-dependent density functional theory (TDDFT) [1] within the usual local (LDA) or semi-local (GGA) approximations has become very popular to calculate excitation energies of medium-sized systems because of its low computational cost and good accuracy.  It has been shown very reliable in predicting excitation energies to the low-lying valence states but still present several shortcomings, especially concerning the underestimation of the high-lying Rydberg excitation energies, a poor description of charge transfer excitations and the lack of double or higher order excitations.  Range separation of the electronic interaction has been proposed as one way to correct these deficiencies and has been shown very efficient when applied to the exchange part of the functional to recover good Rydberg and charge transfer excitation energies [2,3]. However, situations such as the dissociation of the hydrogen molecule and the treatment of excitation with multiple character are still pathological in this approach.  These problems have been attributed to a bad description of the correlation kernel which is frequency independent in TDDFT within the adiabatic approximation.

In this poster, I will present an extension of the range separation technique to the correlation kernel and show a long-range second-order frequency-dependent correlation kernel inspired by the Bethe-Salpeter kernel [4-6] and some numerical results on atoms and molecules.

References

1. M. Casida, in "Recent Advances in Density Functional Methods", D. Chong Eds (1995)
2. Y. Tawada, T. Tsuneda, S. Yanagisawa, T. Yanai and K. Hirao, J. Chem. Phys. 120 8425 (2004)
3. E. Rebolini, A. Savin, J. Toulouse, Mol. Phys. 111, 1219 (2013)
4. P. Romaniello, D. Sangalli, J. A. Berger, F. Sottile, L. G. Molinari, L. Reining, and G. Onida, J. Chem. Phys. 130 044108 (2009)
5. D. Zhang, S. N. Steinmann, and W. Yang, J. Chem. Phys. 139 154109 (2013)
6. E. Rebolini, J. Toulouse, A. Savin, in "Concepts and Methods in Modern Theoretical Chemistry", CRC-Press, 367 (2013)
   

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KM8

Real-time solution of the time-dependent Dirac-Coulomb equation

Marius Kadek1, Lukas Konecny2, Michal Repisky1, Bin Gao1, Kenneth Ruud1, VladimirG. Malkin2, Olga L. Malkina2

1 Centre for Theoretical and Computational Chemistry, Department of Chemistry, University of Troms- The Arctic University of Norway, 9037 Troms, Norway
2 Institute of Inorganic Chemistry, Slovak Academy of Sciences, Dubravska cesta 9, 84536 Bratislava 45, Slovak Republic

In this poster I will outline an approach to solve the time-dependent Hartree-Fock and Kohn-Sham equations with the relativistic four-component Dirac-Coulomb Hamiltonian and demonstrate an application to X-ray spectroscopy. The approach is based on the direct propagation of a one-electron reduced density matrix in the time domain, thus obtaining a non-perturbative solution of the time-dependent equations [1]. We have implemented this method in the ReSpect [2] code (Relativistic Spectroscopy) and performed one-component benchmark calculations. Results on this poster will include the sulfur L2 and L3 edges of the SF6 molecule, where a properly captured splitting of the sulfur p-orbitals due to the spin-orbit interaction will be shown, and the shifts of the fuorine K-edge excitations caused by the relativistic eects [3]. Our results agree well with available experimental data [4].

References

1. M. Repisky, L. Konecny, M. Kadek, V. G. Malkin and O. L. Malkina, in preparation.
2. ReSpect, version 3.3.0 (beta), 2013; Relativistic Spectroscopy DFT program. M. Repisky; S. Komorovsky; V. G. Malkin; O. L. Malkina; M. Kaupp; K. Ruud, with contributions from R. Bast; U. Ekstrom; S. Knecht; O. I. Malkin; E. Malkin(see http://rel-qchem.sav.sk).
3. M. Kadek, M. Repisky, B. Gao, K. Ruud, L. Konecny, V. G. Malkin and O. L. Malkina, in preparation.
4. E. Hudson, D. A. Shirley, M. Domcke, G. Remmers, A. Puschmann, T. Mandel, C. Xue and G. Kaindl. Phys. Rev. A 47 (1993) 361.
   

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