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Measures of ionicity of alkaline-earth oxides from the analysis of ab initio cluster wave functions

Measures of ionicity of alkaline-earth oxides from the analysis of ab initio cluster wave functions We present an analysis of the M -O chemical bonding in the binary oxides MgO, CaO, SrO, BaO, and Al 2 O 3 based on ab initio wave functions. The model used to represent the local environment of a metal cation in the bulk oxide is an M O 6 cluster which also includes the effect of the lattice Madelung potential. The analysis of the wave functions for these clusters leads to the conclusion that all the alkaline-earth oxides must be regarded as highly ionic oxides; however, the ionic character of the oxides decreases as one goes from MgO, almost perfectly ionic, to BaO. In Al 2 O 3 the ionic character is further reduced; however, even in this case, the departure from the ideal, fully ionic, model of Al 3 + is not exceptionally large. These conclusions are based on three measures, a decomposition of the M q + - O q - interaction energy, the number of electrons associated to the oxygen ions as obtained from a projection operator technique, and the analysis of the cation core-level binding energies. The increasing covalent character along the series MgO, CaO, SrO, and BaO is discussed in view of the existing theoretical models and experimental data. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Physical Review B American Physical Society (APS)

Measures of ionicity of alkaline-earth oxides from the analysis of ab initio cluster wave functions

Physical Review B , Volume 48 (16) – Oct 15, 1993
10 pages

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Publisher
American Physical Society (APS)
Copyright
Copyright © 1993 The American Physical Society
ISSN
1095-3795
DOI
10.1103/PhysRevB.48.11573
Publisher site
See Article on Publisher Site

Abstract

We present an analysis of the M -O chemical bonding in the binary oxides MgO, CaO, SrO, BaO, and Al 2 O 3 based on ab initio wave functions. The model used to represent the local environment of a metal cation in the bulk oxide is an M O 6 cluster which also includes the effect of the lattice Madelung potential. The analysis of the wave functions for these clusters leads to the conclusion that all the alkaline-earth oxides must be regarded as highly ionic oxides; however, the ionic character of the oxides decreases as one goes from MgO, almost perfectly ionic, to BaO. In Al 2 O 3 the ionic character is further reduced; however, even in this case, the departure from the ideal, fully ionic, model of Al 3 + is not exceptionally large. These conclusions are based on three measures, a decomposition of the M q + - O q - interaction energy, the number of electrons associated to the oxygen ions as obtained from a projection operator technique, and the analysis of the cation core-level binding energies. The increasing covalent character along the series MgO, CaO, SrO, and BaO is discussed in view of the existing theoretical models and experimental data.

Journal

Physical Review BAmerican Physical Society (APS)

Published: Oct 15, 1993

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