Empirical Potential-Energy Function for Calcium Solids and Clusters
Klas M. Andersson, Roy L. Johnston and John N. Murrell
School of Chemistry and Molecular Sciences, University of Sussex,
Falmer, Brighton BN1 9QJ, United Kingdom.
Article: Physical Review B 1994, 49, 3089-3097.
Abstract
An empirical potential-energy function, consisting of two- and
three-body terms, has been derived for the study of calcium solids and
clusters. With a single set of parameters, this potential reproduces
the phonon frequencies and elastic constants of both the low-temperature
fcc and the high temperature bcc crystalline phases to a high degree of
accuracy. It also gives a sensible energy profile for the tetragonal
(Bain path) interconversion of the two structures, which are both minima
along the path. The potential predicts that the fcc and hcp solids have
almost equal cohesive energies, with that of the bcc phase being 0.02 eV
lower. Other cubic phases and various two-dimensional and
one-dimensional structures have lower cohesive energies. The potential
leads to the conclusion that the most stable clusters tend to be
polytetrahedral, leading to icosahedral packing, thereby maximizing
coordination number.
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