Structural phase transition in a large cluster

The effect of a phase transition between structures in a large cluster with a pair interatomic interaction on the thermodynamic parameters of the clus ter is analyzed. The statistical parameters of a cluster consisting of 923 atoms are determined for an icosahedron and a face-centered cubic (fcc) str ucture. The specific heat and entropy of this cluster are calculated in the case when the transition between the icosahedron and fcc structures has th e greatest effect on these parameters, so that at zero temperature this clu ster has the structure of an icosahedron, and as the temperature increases to the melting point it assumes an fcc structure. Even with this, the contr ibution of the excitations of the atomic configurations to the thermodynami c parameters of a cluster is small compared with the excitation of vibratio ns in the cluster. The contribution of a configurational excitation in the thermodynamic parameters of a cluster becomes substantial for the liquid st ate of clusters. (C) 2000 MAIK "Nauka/Interperiodica".