97-11E

On the basis of proposed earlier model we study the effects of applied uniaxial pressure $\sigma _1-\sigma _2$ on the physical properties of KD$_2$PO$_4$\ ferroelectrics. In the cluster approximation, taking into account the short-range and long-range interactions and the uniaxial stress $\sigma _1-\sigma _2$ we calculate and study thermal, dielectric, and piezoelectric characteristics of a KD$_2$PO$_4$ crystal. A thorough numerical analysis of the obtained results is performed. The temperature and pressure dependences of spontaneous polarization, longitudinal and transverse static dielectric permittivities and piezoelectric coefficients are investigated. The phase transition induced by pressure $\sigma _1-\sigma _2$ is studied.