A THEORETICAL-STUDY OF ORDERING PHENOMENA IN K-IN AND K-SB MOLTEN ALLOYS

The quasilattice approximation (QLA) has been used to study ordering phenomena in K-In and K-Sb alloys. The concentration-concentration fluctuations in the long-wavelength limit S-cc(0), the Warren-Cowley short-range order parameter alpha(1) and the chemical diffusion D have been computed. Our calculations yield, for both alloys, qualitative agreement with experiment in the transition from a compound-forming/phase-separating (CF/PS) state observed in K-In to strong compound formation in the case of K-Sb. Most importantly, we obtain the calculated quantities for the whole concentration range, thus complementing the available experimental evidence. Based on the present work and our previous calculations for K-Te, we predict from an ordering point of view and within the same framework of the QLA, that K-Sn, for which experimental results are not available, would have a lower free energy of mixing and expectedly a stronger tendency for compound formation than that observed in K-Pb.