Global Potentials for Calcium and Strontium Solids
Jason E. Hearn, Roy L. Johnston,* Simona Leoni and John N. Murrell
School of Chemistry and Molecular Sciences, University of Sussex,
Falmer, Brighton BN1 9QJ, United Kingdom.
Article: Journal of the Chemical Society, Faraday
Transactions 1996, 92, 425-432.
Abstract
Empirical two- plus three-body potentials have been derived for calcium and strontium, and applied to the
fcc and bcc structures of both metals. The parameters are derived by fitting phonon frequencies, elastic
constants and other structural data. The potentials obtained give a sensible ordering of solid structures, and
good energy profiles along the (Bain) tetragonal distortion pathway between the fcc and bcc allotropes. The
potentials have been used to calculate the fcc and bcc phonon densities of states (DOS), from which the
Helmholtz energies and the fcc->bcc transition temperatures (T_c) have been evaluated. We
overestimate the value of T_c for Ca and underestimate it for Sr. The potentials give surface
energies which are in good agreement with experiment.
* Present address: School of Chemistry, University of Birmingham, Edgbaston,
Birmingham B15 2TT, UK.
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