Structures and cohesive properties of hydroxides and fluorides calculated using the modified electron gas ionic model |
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Authors: | J A Tossell |
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Institution: | 1. Department of Chemistry University of Maryland, 20742, College Park, Maryland, USA
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Abstract: | Molecular cluster calculations using the purely theoretical modified electron gas (MEG) version of the ionic model predict M-OH and M-F distances with an average error of less than 0.03 Å for a wide range of M cations. Such accuracy compares favorably with that obtained using the more expensive ab initio self-consistent-field molecular orbital (MO) method. The frequencies of totally symmetric stretching vibrations are also predicted with an average error of about 25% using the MEG method but cohesive energies are often in error by large amounts. Cohesive energy errors are highly correlated with electronegativity differences, suggesting that they should be ascribed to ovalent bonding effects. The increase of M-X distance with increasing M coordination number can be simply interpreted in terms of the magnitude and number of M-X attractive and X-X repulsive interactions within the MEG model. |
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