Within the framework of a modified proton ordering model of the KH_{2}PO_{4} family ferroelectric crystals, taking into account a linear over the strain \varepsilon_{6} contribution into the proton system energy, we obtain an expression for longitudinal dynamic dielectric permittivity of a mechanically clamped crystal using the four-particle cluster approximation and the dynamic Glauber approach. At a proper choice of the model parameters, we obtain a good quantitative description of available experimental data for these crystals.
@article{arxiv.1210.2226,
title = {Longitudinal relaxation of mechanically clamped KH_{2}PO_{4} type crystals},
author = {R. R. Levitskii and I. R. Zachek and A. S. Vdovych},
journal= {arXiv preprint arXiv:1210.2226},
year = {2012}
}