Microscopic Interpretation of the Slater Model of Phase Transition in KH₂PO₄-Type Crystals

Abstract

The energy difference between the “up-down” and “lateral” H₂PO₄ configurations in the Slater model is interpreted as a difference in the molecular energies when they are fictitiously isolated while maintaining their configurations in the crystal. This version of the Slater model is shown to be satisfactory for explaining the observed correlation between the transition temperature and the covalent OH(D) bond length of the hydrogen bond OH(D)…O with a reasonable quantitative agreement. It is pointed out that the present model is not applicable to cases where the transition temperatures are very low.