Investigation of the short-range order in the Ca-Sb melts

The thermodynamic functions of formation of the binary Ca-Sb alloys determined in a previous work have been used to elucidate the short-range order in the melts. For this purpose, the regular associated solution model was applied assuming the existence in the liquid phase of hetero-clusters. The integral enthalpy of formation of the melts at 1078 K shows a strong minimum (-67.2 kJ mol(-1) at x(Sb) =0.48) very close to the composition corresponding to the single congruently melting compound of the system (Ca11Sb10). However, it was unrealistic to assume such a large pseudo-molecule in the liquid state and we assume a short-range order based on CaSb. With this assumption, the calculated thermodynamic functions of the melts agree well with the experimental ones. In this paper we give the values of the standard thermodynamic parameters of formation of the associates. (C) 1999 Elsevier Science S.A. All rights reserved.