TY - JOUR
T1 - Density-functional calculation of CeO 2 surfaces and prediction of effects of oxygen partial pressure and temperature on stabilities
AU - Jiang, Yong
AU - Adams, James
AU - Van Schilfgaarde, Mark
N1 - Funding Information:
This paper is based upon work supported by the National Science Foundation under Grant No. NSF-DMI 9974381. Any opinions, findings, conclusions, or recommendations expressed in this paper are those of the authors. The authors wish to thank Dr. Georg Kresse and the VASP group of the University of Vienna, Austria, for their technical assistance with VASP code. One of the authors Y.J. also wishes to acknowledge Dr. William Petuskey, Dr. Peter Crozier, and Dr. Renu Sharma of ASU for helpful discussions. The computational resources of the National Computational Science Alliance (NCSA) at UIUC are also gratefully acknowledged.
PY - 2005/8/8
Y1 - 2005/8/8
N2 - We have used density-functional theory to investigate (111), (110), (210), (211), (100), and (310) surfaces of ceria (Ce O2). Compared with previous interatomic-potential-based studies, our calculations reported a slightly different relative stability ordering and significantly lower surface energies for the stoichiometric surfaces. Using a defect model, the surface stabilities were evaluated as functions of oxygen partial pressure and temperature. Our investigations were restricted to ideal surface terminations, without considering defect formation on those surfaces. We found that at 300 K, the stoichiometric (111) has the lowest free energy for a wide range of oxygen partial pressures up to 1 atm, and only at ultrahigh vacuum does the Ce-terminated (111) becomes the most stable one. The transition point for the Ce-terminated (111) surfaces moves to higher oxygen partial pressures when temperature increases. To improve the prediction of electron density of states, we used the local-density approximation plus U (J) correction method to correct the on-site Coulomb correlation and exchange interaction due to the strongly localized Ce-4f electrons. The optimal parameter combination of U=7 eV and J=0.7 eV was found to improve the O 2p-Ce 4f gap without much degradation of ground-state bulk properties or the O 2p-Ce 5d gap. The bulk and surface electronic structures were then analyzed based on the improved density of states.
AB - We have used density-functional theory to investigate (111), (110), (210), (211), (100), and (310) surfaces of ceria (Ce O2). Compared with previous interatomic-potential-based studies, our calculations reported a slightly different relative stability ordering and significantly lower surface energies for the stoichiometric surfaces. Using a defect model, the surface stabilities were evaluated as functions of oxygen partial pressure and temperature. Our investigations were restricted to ideal surface terminations, without considering defect formation on those surfaces. We found that at 300 K, the stoichiometric (111) has the lowest free energy for a wide range of oxygen partial pressures up to 1 atm, and only at ultrahigh vacuum does the Ce-terminated (111) becomes the most stable one. The transition point for the Ce-terminated (111) surfaces moves to higher oxygen partial pressures when temperature increases. To improve the prediction of electron density of states, we used the local-density approximation plus U (J) correction method to correct the on-site Coulomb correlation and exchange interaction due to the strongly localized Ce-4f electrons. The optimal parameter combination of U=7 eV and J=0.7 eV was found to improve the O 2p-Ce 4f gap without much degradation of ground-state bulk properties or the O 2p-Ce 5d gap. The bulk and surface electronic structures were then analyzed based on the improved density of states.
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U2 - 10.1063/1.1949189
DO - 10.1063/1.1949189
M3 - Article
AN - SCOPUS:24144432327
SN - 0021-9606
VL - 123
JO - Journal of Chemical Physics
JF - Journal of Chemical Physics
IS - 6
M1 - 064701
ER -