Abstract
Uniaxial pressure influence on the phase transition of deuterated (0-90%) TGS crystals are reported for the three directions- a, b, c*. The coefficients γi (γi ≏ ∂Tc/∂xi) are established to be lineary dependent on the uniaxial pressure. The coefficient ξ of the fourth power of P in the free energy expansion is practically uniaxial pressure independent. The main changes of γi observed in the ac* plane are related to “long” O-H-O and N-H-O bonds. The values of the γi coefficients are in well agreement with those calculated from the Ehrenfest relation.