Orientationally Disordered Mixed Crystals Sharing Methylchloromethanes [(CH3)4-nCCln, n = 0, ..., 4

Abstract

The experimental systems studied are the five methylchloromethanes [(CH 3 ) 4 - n CCl n , n = 0, ..., 4] and seven of their binary combinations, the accent being on the thermodynamic mixing properties in the plastic crystalline (orientationally disordered) state with its three forms (rhombohedral, face-centered cubic and simple cubic). It is demonstrated that a uniform description can be given of the thermodynamic excess properties characterized by a uniform temperature (420 K) of enthalpy/entropy compensation. The magnitude of the excess properties is related to volumetric mismatch between the components of a system, and, to a relatively small extent, to the dipolar nature of the molecules.