Inelastic neutron scattering to very high pressures

Progress in high-pressure and neutron scattering methods has recently allow ed measurements of phonon dispersion curves of simple solids at high pressu res to 10 GPa. In this technique single crystals of 10-25 mm(3) volume are compressed by the Paris-Edinburgh cell and the phonon frequencies are measu red on high-flux triple axis spectrometers. Detailed studies of the lattice dynamics of low-compressible systems are feasible, including measurements of mode Gruneisen parameters, elastic constants, and precursor effects of p hase transitions. We describe the experimental set-up and illustrate its po tential by results on semiconductors (Ge and GaSb) and metals (Fe and Zn) o btained at the LLB (Saclay) and ILL (Grenoble) reactor sources.