The mean-field analysis of Sn2P2(SexS1-x)6 thermodynamical properties in the paraelectric, incommensurate and ferroelectric phases

Abstract

In the meanfield approximation, assuming the linear concentration dependence of the thermodynamic potential coecients and taking into account the higher harmonics of spatial order parameter modulation in the incommensurate phase and interaction between order parameter and elastic deformation, the temperature and concentrational dependencies of the principal thermodynamical characteristics of Sn2P2(SexS1-x )6 uniaxial ferroelectrics are calculated and compared with the experimental data. Some discrepancy exists at the quantitative comparison of calculated and experimental data for the temperature dependencies of heat capacity, amplitude and wave vector of modulation, essentially in the vicinity of the lock{in phase transition in incommensurate phase.