PHONONS IN SILVER GALLIUM DISELENIDE

The dispersion curves along the directions [100] and [001] of AgGaSe2 have been measured by inelastic neutron scattering. The results are an alysed with different rigid-ion models: Born-von Karman and valence fo rce held models, which give a good agreement with experiments. Additio nal measurements of the acoustical branches allow us to determine elas tic stiffness constants which are (x10(10) N m(-2)) c(11) = 8.01, c(33 ) = 7.07, C-44 = 2.12, C-66 = 2.47, C-12 = 5.16, c(13) = 5.26. The com pressibility calculated from these constants is in accordance with the experimental value.