Thermodynamic properties and local structures of non-stoichiometry. Galvanic cell study of fused InxI1–x mixtures

Abstract

Thermodynamic studies of fused non-stoichiometric InxI1–x mixtures have been carried out by determining the partial thermodynamic parameters of the In component using a galvanic cell method. The integral entropy and enthalpy of mixing were computed with the mixtures as fused In(xr)+ InI3(1 –xr). As a further effort to determine the ionic arrangements the long-wavelength limit of the concentration correlation function, Scc(0), was calculated and developed to examine the crude short range ordering, ΔNα, and the role of charge transfer, ΔeIn. Large deviations were seen in all the thermodynamic parameters and in the above-mentioned structure parameters for these molten metal + non-metal mixtures, in particular near the stoichiometric composition InI2(x= 0.333 or xr= 0.333). These marked composition trends have been interpreted as a consequence of there being two different electronic states for In (i.e., InI–4 and In+) or of the covalent and ionic bondings between unlike nearest neighbours in the vicinity of InI2.