Atomic heats of tin and tin-indium

Abstract

Thermodynamic data for crystalline white and grey tin were assessed using an extended Einstein model from 0 K. Ab-initio simulations in the framework of density functional theory (DFT) with the quasiharmonic approximation (QHA) were carried out to define the heat capacities for both phases of tin from 0 K up to room temperatures. Good agreement was observed between theoretical and experimental heat capacities, which makes it possible to combine theoretical and experimental data to determine the standard entropies. Data for the liquid phase were described using a two state model. During the assessment, careful analysis of the experimental data was carried out. In order to fulfil the need for a precise evaluation of So298 we needed to use an additional technique using multiple Einstein functions, which allows the experimental heat capacity and enthalpy data for the solid phase to be approximated accurately from 0 K up to the melting point and to estimate solid phase transition entropy and enthalpy which are difficult to measure due to a high activation barrier. Additional measurements of heat capacity were carried out where existing data were scarce.