Effect of pressure on the phonon properties of europium chalcogenides

Lattice vibrational properties of europium chalcogenides have been investig ated at high pressure by using a simple lattice dynamical model theory viz. the three-body force rigid ion model (TRIM) which includes long range thre e-body interaction arising due to charge transfer effects. The dispersion c urves for the four Eu-chalcogenides agree reasonably well with the availabl e experimental data. Variation of LO, TO, LA and TA phonons with pressure h ave also been studied at the symmetry points of the brillouin zone (BZ) for Eu-chalcogenides for the first time by using a lattice dynamical model the ory. We have also calculated the one phonon density of states and compared them with the first order Raman scattering results. The calculation of one phonon density of states for Eu-chalcogenides has also been extended up to the phase transition pressure. We observed a pronounced shift in phonon spe ctrum as pressure is increased.