Title: LATTICE DYNAMICS OF A MONOCLINIC CsH$_{\bf 2}$PO$_{\bf 4}$ CRYSTAL
Authors: Ya.I.Shchur (Institute of Physical Optics, 23 Dragomanov Str., 290005 Lviv, Ukraine), R.R.Levitskii (Institute for Condensed Matter Physics of the National Academy of Sciences of Ukraine, 1 Svientsitskii Str., 290011 Lviv, Ukraine), O.G.Vlokh, A.V.Kityk (Institute of Physical Optics, 23 Dragomanov Str., 290005 Lviv, Ukraine), Y.M.Vysochansky, A.A.Grabar (Uzhgorod State University, 46 Pidhirna Str., 294000 Uzhgorod, Ukraine)

The phonon dispersion relations in a CsH$_2$PO$_4$ crystal in a paraelectric phase by means of a rigid molecular-ion model are calculated. The phonon spectra in the quasi-harmonic approximation at various values of temperature and hydrostatic pressure are obtained. The condensation of A$_u$ external phonon branch in the centre and at the boundary of the Brillouin zone is obtained.

Comments: Figs. 7, Refs. 38, Tabs. 6.