Comparison of the bulk and surface properties of ceria and zirconia by ab initio investigations
Quantum mechanical (QM) calculations were made at a periodic Hartree-Fock (HF) level, on the bulk and surface properties of cubic CeO{sub 2} and ZrO{sub 2}. The authors have investigated the M-O bonding features, and established the high degree of ionicity of both materials, which is greater for CeO{sub 2} than ZrO{sub 2}. The calculated values for the C{sub 11}, C{sub 12}, and C{sub 44} elastic constants, are in close agreement with experiment; an extended oxygen basis set, containing d-orbital polarization functions, is essential to model accurately the symmetry lowering during the C{sub 44} distortion. In the surface studies, they have calculated the surface energies of the {l{underscore}brace}011{r{underscore}brace} and {l{underscore}brace}111{r{underscore}brace} faces of both ceria and zirconia. QM results are compared with interatomic potential-based (IP) methods to assess the accuracy of the latter. IP methods were found to provide a correct estimate of the surface relaxations and the correct order of stability of the two faces examined, with the energy difference between the {l{underscore}brace}011{r{underscore}brace} and the {l{underscore}brace}111{r{underscore}brace} surfaces being approximately 1 J/m{sup 2}, as in the QM study. However, IP methods do not always discriminate adequately between the properties of the two materials. Finally, geometric and electronic relaxations in the {l{underscore}brace}111{r{underscore}brace} surface are confined to the outermost oxygen ions, while in the {l{underscore}brace}011{r{underscore}brace} slabs they are more important and extend to the subsurface layers in a columnar way. The unsaturation of the surface ions in the {l{underscore}brace}011{r{underscore}brace} face may have important implications for the catalytic activity of the materials.
- Research Organization:
- Royal Institution of Great Britain, London (GB)
- OSTI ID:
- 20013099
- Journal Information:
- Journal of Physical Chemistry B: Materials, Surfaces, Interfaces, amp Biophysical, Vol. 103, Issue 46; Other Information: PBD: 18 Nov 1999; ISSN 1089-5647
- Country of Publication:
- United States
- Language:
- English
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