Normal Modes of Vibrations in CuCl

Abstract

The frequency-wave-vector dispersion relation v(q) for the normal vibrations of a CuCl single crystal at room temperature has been measured for the [100]-, [110]~, and [lllj-symmetric directions using inelastic neutron scattering.In view of the interest in studying the lattice dynamics of crystals with zinc-blende structure, we present in this paper the results of coherent inelastic neutron scattering on cuprous chloride (CuCl). Our particular attention was drawn by this material because of its peculiar behavior relative to other crystals with the same symmetry, as pointed out by Martin. 1 The present experiments were performed by means of the triple-axis crystal spectrometer at 400-300 '200H 100-the EL3 reactor, Saclay. A collimated beam of monochromatic neutrons, produced by Bragg reflection from a germanium single crystal, was incident upon the CuCl specimen. The energies of the scattered neutrons were determined by Bragg reflection from a second germanium single crystal. The experiments were carried out by using either constant-Q or constant-v techniques, for waves propagating along the high-symmetry directions [lOO], [llO], and [ill]. 200-r=15min jM50-100-50 H y>-const"anl-= 20cm" TA [&S]Q-consfar^ = 0.6

Temperature Dependence of Raman Spectra of Cuprous Halides

“…As is clear in the phonon dispersion of CuC1, we must choose the optical LO phonon as one of the scattering phonons. But the wave vector dependence of the LO phonon frequency is quite small [3], and then the contribution from other points satisfying energy conservation would give almost the same representation as (nlo-n220). All the possible contributions from other points will be eventually included in the (nlo-n220) term whose coefficient is obtained so as to f i t the experimental data.…”

First and second order Raman scattering of monocrystalline CuCl

“…Simultaneously, we presented [5] a preliminary study on the Raman spectrum of the three Cu halides at two temperatures but without polarization effects. A great similarity in the three spectra was underlined and we explained the four lines with the help of neutron scattering experiments [6]. Another study [7] on oriented monocrystals and with different polarizations of both incident and scattered light was briefly reported, the results of which being consistent with the previous observations.…”

On the energy band structure and the phase transitions in a cuprous chloride crystal

“…I n view of the large increase of the elastic anisotropy [4] in the ( 110) directions and the anomaly of the phonon spectra [20] of CuCl in the vicinity of the X-point, it was reasonable to assign this lowest conduction band minimum to the X-point. [17]) is a t the r-point, the smallest admixture a t the X-points.…”