Title: INFLUENCE OF \sigma_1-\sigma_2 STRESS ON PHASE TRANSITION AND PHYSICAL PROPERTIES OF KD_2PO_4-TYPE FERROELECTRICS
Author(s): I.V.Stasyuk (Institute for Condensed Matter Physics of the National Academy of Sciences of Ukraine, 1 Svientsitskii Str., 79011 Lviv, Ukraine), R.R.Levitskii (Institute for Condensed Matter Physics of the National Academy of Sciences of Ukraine, 1 Svientsitskii Str., 79011 Lviv, Ukraine), I.R.Zachek (State University ``Lvivska Politekhnika'', 12 Bandera Str., 79013 Lviv, Ukraine), A.S.Duda (Institute for Condensed Matter Physics of the National Academy of Sciences of Ukraine, 1 Svientsitskii Str., 79011 Lviv, Ukraine)

Within the proposed earlier model we study effects of stress $\sigma_1-\sigma_2$ on the \dkdp type ferroelectrics. In the cluster approximation for the short-range correlations, we calculate dielectric, piezoelectric, and elastic characteristics of a strained by $\sigma_1-\sigma_2$ \dkdp type crystal. Numerical analysis of the obtained results is performed. Stress dependences of the calculated characteristics and the phase diagram are explored. Possibility of the induced by $\sigma_1-\sigma_2$ phase transition into a new paraelectric phase with monoclinic symmetry is discussed.

Key words: shear stress, monoclinic phase, phase diagram, piezoelectricity, strain, KDP
PACS: 77.80.-e, 77.80.Bh, 77.84.Fa