Temperature dependence of interatomic separation

A simple unification of various relations for the temperature dependence of interatomic separation is presented. It is found that the relations reported by the earlier workers as new are contained in a simple thermodynamic relation. Some other relations based on different physical origins are also included in the study and compared with the thermodynamic relation. The results are reported for ten crystals, viz. KF, KCl, KBr, KI, RbF, RbCl, RbBr, RbI, MgO and CaO. A good agreement between unified relation and experiment demonstrates the superiority of the simple theory based on the thermodynamic analysis.