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

The thermodynamic functions of formation of the binary Ca-Sb alloys determi ned 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 app lied assuming the existence in the liquid phase of hetero-clusters. The int egral 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 correspondin g to the single congruently melting compound of the system (Ca11Sb10). Howe ver, it was unrealistic to assume such a large pseudo-molecule in the liqui d state and we assume a short-range order based on CaSb. With this assumpti on, the calculated thermodynamic functions of the melts agree well with the experimental ones. In this paper we give the values of the standard thermo dynamic parameters of formation of the associates. (C) 1999 Elsevier Scienc e S.A. All rights reserved.