High pressure studies of the phase transition in the ferroelectric Sn2P2S6

We apply a method of pulse-adiabatic modulation of pressure to obtain heat capacity and thermal expansion of ferroelectric Sn2P2S6 in the vicinity of the second order phase transition at pressures to 5 kbar. The phase transition in Sn2P2S6 does not change its nature and stays second order in the whole range of pressure currently studied. The earlier conclusion on the tricritical features of the phase transition in Sn2P2S6 cannot be confirmed. Discontinuities of heat capacity and thermal expansion perfectly fit the Ehrenfest equation that expected in the mean field theories. An excellent performance of the Ehrenfest formula in a wide range of pressures establishes phase transition in Sn2P2S6 as an almost ideal mean field phase transition.