Km. Andersson et al., EMPIRICAL POTENTIAL-ENERGY FUNCTION FOR CALCIUM SOLIDS AND CLUSTERS, Physical review. B, Condensed matter, 49(5), 1994, pp. 3089-3097
An empirical potential-energy function, consisting of two- and three-b
ody terms, has been derived for the study of calcium solids and cluste
rs. With a single set of parameters, this potential reproduces the pho
non frequencies and elastic constants of both the low-temperature fee
and the high-temperature bcc crystalline phases to a high degree of ac
curacy. It also gives a sensible energy profile for the tetragonal (Ba
in path) interconversion of the two structures, which are both minima
along the path. The potential predicts that the fee and hcp solids hav
e almost equal cohesive energies, with that of the bcc phase being 0.0
2 eV lower. Other cubic phases and various two-dimensional and one-dim
ensional structures have lower cohesive energies. The potential leads
to the conclusion that the most stable clusters tend to be polytetrahe
dral, leading to icosahedral packing, thereby maximizing coordination
number.