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 language | English |
|---|---|
| Article number | 214705 |
| Journal | Journal of Chemical Physics |
| Volume | 127 |
| Issue number | 21 |
| DOIs | |
| Publication status | Published - 2007 Dec 17 |
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ASJC Scopus subject areas
- Physics and Astronomy(all)
- Physical and Theoretical Chemistry
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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 journal › Article
}
TY - JOUR
T1 - Electronic and vibrational properties of nickel sulfides from first principles
AU - Wang, Jeng-Han
AU - Cheng, Zhe
AU - Bŕdas, Jean Luc
AU - Liu, Meilin
PY - 2007/12/17
Y1 - 2007/12/17
N2 - 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.
AB - 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.
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U2 - 10.1063/1.2801985
DO - 10.1063/1.2801985
M3 - Article
AN - SCOPUS:36949002251
VL - 127
JO - Journal of Chemical Physics
JF - Journal of Chemical Physics
SN - 0021-9606
IS - 21
M1 - 214705
ER -