ACTINIDE COMPOUNDS UNDER PRESSURE

An overview of pressure-induced structural phase transitions and compressibility of actinide compounds will be given. Systematic trends in the nature of the high-pressure phases, the transition pressures, the hysteresis to retransformation on pressure release, and the compressibility are observed in the family of AnX compounds of B1 (NaCl) structure type. The dioxides studied up to now form high-pressure phases of PbCl2 type. UX2 compounds of Fe2As type also tend to have PbCl2 type high-pressure phases. The Th3P4 type compounds studied up to now did not transform up to 50 GPa. The same is true for ThOS and UOSe up to about 45 GPa. Comparison with rare earth compounds will be made where possible.