Brillouin scattering by molecular crystals: s-trichlorobenzene

Abstract

The Raman and Brillouin scattering spectra of single crystal s‐trichlorobenzene at room temperature, and the Raman spectrum of a polycrystalline sample at low temperatures, have been obtained. Seventeen of the 21 predicted lattice vibrations have been observed in the Raman spectrum. Brillouin spectra at various angles of scattering and for various crystal orientations have yielded sound velocities for 11 modes of propagation. The nine independent elastic constants for the orthorhombic crystal have been evaluated. The dynamic and static properties of the crystal lattice have been calculated using an atom–atom intermolecular potential model with parameters derived by Bonadeo. Agreement with the Raman lattice frequencies is to about 7%, with the observed sound velocities to about 9%. The atom–atom potential is capable of predicting dynamic and static properties of the lattice with reasonable accuracy, but is apparently not completely adequate.