Abstract
The crystal structure of ThS2, ThSe2 and US2 has been investigated for pressure up to 60GPa using x-ray powder diffraction. The bulk moduli are 175(10), 155(10) and 155(20) GPa, respectively. A pressure-induced phase transformation occurs at about 40 GPa for ThS2, 30 GPa for ThSe2 and 15 GPa for US2. The results for ThSe2 indicate that its high-pressure phase has a monoclinic structure. The same structure is compatible with the observed high-pressure spectra of ThS2 and US2. However, the crystal system assignment is less certain for these compounds.