The modified two-sublattice pseudospin lattice coupled mode model Hamiltonian is extended by adding third- and fourth-order phonon anharmonic interactions, extra spin–lattice interactions, direct spin–spin interaction and an applied electric field terms considered for the study of deuterated Rochelle salt crystal. The double-time thermal-dependent Green function, Dyson equation and symmetric decoupling scheme have been used to derive the expressions for energy shift, line width, ferroelectric soft mode frequency, dielectric constant, dielectric tangent loss and spontaneous polarization. Model values of various physical parameters are fitted in the obtained expressions; the thermal variations of ferroelectric soft mode frequency, dielectric constant, loss tangent and spontaneous polarization have been calculated for deuterated Rochelle salt crystal. Theoretical results with model values compare well with experimental data reported by others for deuterated Rochelle salt. Our expressions contain all possible interactions as compared to the earlier authors.

通过添加三阶和四阶声子非调和相互作用，额外的自旋-晶格相互作用，直接自旋-自旋相互作用以及为研究罗谢尔盐研究而考虑的外加电场项，扩展了修正的两子格伪自旋晶格耦合模式哈密顿量模型。水晶。通过使用与热相关的二次格林函数，戴森方程和对称解耦方案来导出能量位移，线宽，铁电软模频率，介电常数，介电切线损耗和自发极化的表达式。各种物理参数的模型值拟合在获得的表达式中；计算了氘代罗谢尔盐晶体的铁电软模频率，介电常数，损耗角正切和自发极化的热变化。具有模型值的理论结果与氘代罗谢尔盐的其他实验结果进行了很好的比较。与早期作者相比，我们的表达式包含所有可能的交互。