11-18U

Within modified proton ordering model of quasi-one-dimensional CsH$_2$PO$_4$ type ferroelectrics with hydrogen bonds with taking into account linear on strains $\varepsilon _i$ and $\varepsilon _5$ contributions into energy of proton system, but without taking into account tunneling, within the two-particle cluster approximation the effect of hydrostatic and uniaxial pressures on phase transition and physical characteristics of quasi-one-dimensional CsH$_2$PO$_4$ type ferroelectrics are studied and calculated. At the proper set of the parameters good quantitative description of the corresponding experimental data for those crystals is obtained.