Acoustic analogs of elasticity theory ratios for determining anisotropic Poisson ratios of cubic monocrystals

The authors suggests new parameters for determining anisotropie Poisson´s ratios a_<;hkt>; of cubic crystals representing combinations of squared ratios of longitudinal and transverse elastic waves velocities along crystallographic directions <;100>; and <;110>;. We showed types of parameter and Poisson´s ratio changes in the crystals of solid solutions Sm_1-xY_xS which undergo isostructural (NaCl-NaCl) electron (semiconductor-metal) phase transition of the 1^st type under the critical concentration of x_c = 0.15.