Beyond the Rigid-Ion Approximation with Spherically Symmetric Ions

Boyer, L. L.; Mehl, M. J.; Feldman, J. L.; Hardy, J. R.; Flocken, J. W.; Fong, C. Y.

doi:10.1103/physrevlett.57.2331.4

Cited by 13 publications

(2 citation statements)

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“…It is thus reasonable to account for short range effects by considering the bond lengths of bonded and non-bonded contacts and the bond angles as regressors for the ESCD coefficients. Long range effects can be accounted for by using the site potential as a regressor as is done in the PIB 1~ model (Boyer et al 1985;Cohen et al 1987a, b). If restricting to a quadratic form without cross terms the following basic regression model is obtained:…”

Section: Regression Of Escd Model Parametersmentioning

confidence: 99%

The ionic model: Extension to spatial charge distributions, derivation of an interaction potential for silica polymorphs

1995

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Abstract. An interatomic interaction potential for silica polymorphs is derived based on the SCD model (cfr. Tijskens et al. 1994). This interaction potential incorporates all classical electrostatic interactions arising from the spherical part of the spatial extent of the atoms including many body interactions. The potential is derived from Hartree-Fock energies and electron densities for a set 72 [8i04] 4--and [Si207]6--clusters with variable configuration. The long range impact of the surroundings on these clusters in the infinite system has been successfully mimicked by embedding the clusters in a finite three-dimensional array of point charges. This three-dimensional array of point charges is optimized as to reproduce the average site potential and its gradient occurring in II-IVcoordinated silica polymorphs at the central atoms of the clusters. The resulting interaction potential consists of two functions of the configurational coordinates, ~, describing spherical "atomic" electron densities, (YA(X, N) for A = Si, O. All classical electrostatic interactions are derived from these densities. A Born-Mayer type correction term AEqm(~) models the quantum mechanical interactions and the electrostatic interactions arising from the non-spherosymmetrical component of the electron density. The new interaction potential model shows a slightly improved reproduction of the potential surface with respect to the classical Born-Mayer ionic model and demonstrates the importance of many body interactions as charge transfer and expansion/contraction of the atomic electron densities in these systems. Also the dependence of the quantum mechanical correction term AEqm(~ ) on the Si--O--Si-bond angle proves covalent effects to be larger than suggested by the classical BornMayer ionic model thereby clarifying the controversy in literature on the importance of covalent effects in silica polymorphs and polymerised silicates in general.

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Section: Regression Of Escd Model Parametersmentioning

confidence: 99%

The ionic model: Extension to spatial charge distributions, derivation of an interaction potential for silica polymorphs

1995

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“…This inability has led to somewhat of an impasse in the atomistic modeling in that, although much effort has been put into modeling Al 2 O 3 , it has been largely concentrated on this specific problem. 3 The potential-induced breathing model (PIB) 16 goes beyond the shell model by allowing for the spherical relaxation of the anion charge density calculated via a Watson sphere method. To date, two versions have been tested on the various possible M 2 O 3 structures, based on the Thomas-Fermi (PIB-TF) and the Kohn-Sham (PIB-KS) kinetic-energy functionals.…”

Section: Introductionmentioning

confidence: 99%

High‐Pressure Phase Behavior of Alumina: Predictions of a Transferable Ionic Potential Model

Wilson

1998

Journal of the American Ceramic Society

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A recently introduced potential model for alumina has been used to study a wider range of structures than previously attempted. The model contains both the spherical relaxation of, and induced dipoles and quadrupoles on, the oxide anions. The model is applied to the possible high-pressure phase transition from the ground-state corundum structure to the Rh 2 O 3 -II structure. A transition pressure of 194 GPa has been predicted, which is in excellent agreement with the most-recent experimental results. The spherical relaxation and induced quadrupoles are crucial in effectively modeling the transition. The shortcomings of the model are assessed by comparison with experiment and both ab initio and model calculations. Other structures common in this stoichiometry have also been considered.

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