A model evaluation of entropies and related thermal quantities of alkali halides based on a generalised bonding scheme

A statistical-mechanical model for the entropy of charged hard-sphere mixture having arbitrary charges and sizes, based on a generalised bonding scheme, is applied to evaluate entropies and related thermal quantities of alkali halides, treating these compounds as large fractional charge-transferred ionic systems, where bonds in these hetero-diatomic molecules are modelled as a combination of strong partially charge-transferred ionic and feeble fractional covalent bonds. The computed theoretical results are in excellent agreement with the experimental data. This work has precisely incorporated the charging entropy contribution, opening an alternate approach for picturing bonds in hetero-diatomic univalent molecules.