Electronic and vibrational properties of nickel sulfides from first principles

Jeng-Han Wang, Zhe Cheng, Jean Luc Bŕdas, Meilin Liu

Research output: Contribution to journalArticle

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Abstract

We report the results of first-principles calculations (generalized gradient approximation-Perdew Wang 1991) on the electronic and vibrational properties of several nickel sulfides that are observed on Ni-based anodes in solid oxide fuel cells (SOFCs) upon exposure to H2 S contaminated fuels: heazlewoodite Ni3 S2, millerite NiS, polydymite Ni3 S4, and pyrite Ni S2. The optimized lattice parameters of these sulfides are within 1% of the values determined from x-ray diffraction. The electronic structure analysis indicates that all Ni-S bonds are strongly covalent. Furthermore, it is found that the nickel d orbitals shift downward in energy, whereas the sulfur p orbitals shift upward with increasing sulfur content; this is consistent with the decrease in conductivity and catalytic activity of sulfur-contaminated Ni-based electrodes (or degradation in SOFC performance). In addition, we systematically analyze the classifications of the vibrational modes at the point from the crystal symmetry and calculate the corresponding vibrational frequencies from the optimized lattice constants. This information is vital to the identification with in situ vibrational spectroscopy of the nickel sulfides formed on Ni-based electrodes under the conditions for SOFC operation. Finally, the effect of thermal expansion on frequency calculations for the Ni3 S2 system is also briefly examined.

Original languageEnglish
Article number214705
JournalJournal of Chemical Physics
Volume127
Issue number21
DOIs
Publication statusPublished - 2007 Dec 17

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solid oxide fuel cells
Solid oxide fuel cells (SOFC)
Sulfur
sulfides
sulfur
nickel
Lattice constants
electronics
orbitals
Vibrational spectroscopy
Electrodes
electrodes
shift
Crystal symmetry
Sulfides
Vibrational spectra
pyrites
Nickel
Electronic structure
Thermal expansion

ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

Cite this

Electronic and vibrational properties of nickel sulfides from first principles. / Wang, Jeng-Han; Cheng, Zhe; Bŕdas, Jean Luc; Liu, Meilin.

In: Journal of Chemical Physics, Vol. 127, No. 21, 214705, 17.12.2007.

Research output: Contribution to journalArticle

Wang, Jeng-Han ; Cheng, Zhe ; Bŕdas, Jean Luc ; Liu, Meilin. / Electronic and vibrational properties of nickel sulfides from first principles. In: Journal of Chemical Physics. 2007 ; Vol. 127, No. 21.
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