20-05U

For investigation of effects appearing under influence of mechanical stresses and electric fields we use a model of glycinium phosphite ferroelectric  modified by taking into account of piezoelectric coupling of structure elements, which order in this crystal, with lattice strain. Within two-particle cluster approximation the components of polarization vector and dielectric permittivity tensor of the crystal, as well as  its piezoelectric, elastic and thermal characteristics are calculated. The influence of shear stresses,  hydrostatic and uniaxial pressures, as well as longitudinal and transverse electric fields on the phase transition and physical characteristics of the crystal is studied. Longitudinal and transverse electrocaloric effects in the crystal are calculated.