Regular Trends in Variation of Crystal Structures of Actinide Metals and Their Alloys

The regular trends in variation of crystal structures of 5f actinide metals in their alloys, under theaction of a high pressure, also in alloys of 4f lanthanide metals with plutonium can by explained by par-ticipation of 5f electrons in formation of the interatomic bond. By analogy with the criterion R _m R _4f (the ratio of "metallic" radius R _m to the radius of 4f shell), used for lanthanide metals, the ratio of the metallic radius to the radius of the trivalent ion (R _m/R ^{3 +}) was selected as a measure of this participation. The changes occurring in crystal lattices of americium, curium, and samarium in their alloys with plutonium, phase transitions in transplutonium metals under a high pressure, and also the order of variation of metallic radii along the actinide series are considered.