Title: Effect of hydrostatic pressure and longitudinal electric field on phase transitions and thermodynamic characteristics of quasione-dimensional CsH₂PO₄ ferroelectric
Author(s):

	A.S. Vdovych (Institute for Condensed Matter Physics of the National Academy of Sciences of Ukraine, 1 Svientsitskii St., 79011 Lviv, Ukraine),
	I.R. Zachek (Lviv Polytechnic National University, 1 S. Bandera St., 79013, Lviv, Ukraine),
	R.R. Levitskii (Institute for Condensed Matter Physics of the National Academy of Sciences of Ukraine, 1 Svientsitskii St., 79011 Lviv, Ukraine)

We propose a two-sublattice proton ordering model for the quasione-dimensional CsH₂PO₄ ferroelectric with hydrogen bonds, which takes into account linear on lattice strains u₁, u₂, u₃ and u₅ contribution to the energy of proton subsystem. The model also takes into account the dependence of effective dipole moments of pseudospins on the order parameters, which enables one to agree the effective dipole moments in paraelectric and ferroelectric phases. Within this model in two-particle cluster approximation on short-range interactions and in the mean field approximation on long-range interactions, there is investigated the behaviour of spontaneous polarization, longitudinal dielectric permittivity and molar heat capacity under the action of hydrostatic pressure and longitudinal electric field. The phase transition into antiferroelectric phase under high pressures is explained. The character of smearing of the paraelectric-ferroelectric phase transition as well as suppression of the antiferroelectric phase at the presence of electric field is studied.

Key words: ferroelectrics, phase transitions, dielectric permittivity, hydrostatic pressure effect, electric field effect

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