20-11U

Within a deformed two-sublattice proton ordering model for the quasione-dimensional CsH₂PO₄ ferroelectric with hydrogen bonds, in two-particle cluster approximation on short-range interactions and in mean field approximation on long-range interactions it is calculated behaviour of spontaneous polarization, longitudinal dielectric permittivity, piezoelectric, elastic characteristics and molar heat capacity under influence of hydrostatic pressure. Character of smearing of the phase transition from paraelectric to ferroelectric phase under influence of the longitudinal electric field is investigated.