Monoclinic elastic and piezoelectric properties of Rochelle salt. Description within the modified Mitsui model

We propose a modification of the two-sublattice Mitsui model that takes into account a coupling with diagonal components of the strain tensor. Within the developed model, we calculate the piezoelectric and elastic characteristics of Rochelle salt related to those strains. In the approximation of zero thermal expansion, we find a set of the model parameters providing a satisfactory agreement with the available experimental data for the elastic constants cEij and cEi4 and for the piezoelectric constants d1j and g1j.