Influence of external electric field on incommensurate-commensurate phase transition in K₂SeO₄and (NH₄)₂BeF₄crystals. I. Static properties

Abstract

The author presents a study of the influence of an external electric field on the incommensurate-commensurate phase transition in K2SeO4- and (NH4)2BeF4-like crystals. Within the constant-amplitude approximation the same type of thermodynamic potential is found in both cases. The phase diagram in the E-T phase plane is found and should exhibit a Lifshitz point. The susceptibility of the incommensurate phase diverges at the transition point while that of the commensurate phase remains finite.