Crystallography and the phase rule

Publisher Website
Google Scholar
Abstract
Classical thermodynamics provides powerful methods for correlating various thermal parameters of a system. However, anomalies are found in the classical theory particularly for condensed phases, such as solids or liquids. A detailed study of the structure of such phases by what may be broadly termed crystallographic methods has thrown much light on the classical anomalies. The present review surveys various structural changes such as crystal lattice transformations or melting that produce increases of entropy and thus can favour thermodynamic transitions in solids. Particular attention is directed towards the structural elucidation of the following anomalies. Pre-transition and pre-melting phenomena. In many cases these can now be attributed to gradual structural changes within a crystal of the same kind as the discontinuous jump at a transition. The occurrence of smeared or continuous thermodynamic transitions, which are sometimes described as transitions of "higher order." These can often now be attributed to the coexistence of regions of two slightly different structures or sub-units within a hybrid single crystal. Reference is made to some of the techniques of study that have been used to investigate such coexistence. The occurrence of hysteresis around a thermodynamic transition. This can arise from the same coexistence phenomena that lead to smeared thermodynamic transitions. Precision studies on single crystals of the kinds described seem likely to throw much light on thermodynamic transitions in solids.

This publication has 62 references indexed in Scilit: