Abstract
The UAI2, UAI2, AND UAI4 compounds have been studied by high pressure X-ray diffraction up to a maximum pressure of ∼ 35 GPa. The compressibility behaviour of UAI2 has been found to be consistent with the itinerant 5f states, whereas that of UAI2 and UAI4, indicate a more localized nature. Further, UAI2 has been found to undergo a structural transition at ∼ 11 GPa and the structure of the high pressure phase has been identified to be of MgNi2 type with space group P63/mmc. The structure of UAI2 at ambient pressure is of MgCu2 type with space group Fd3m. From the electronic considerations, for instance, free electrons per atom ratio e/a, it is anticipated that it may transform back to MgCu2 type structure at still higher pressures. On similar considerations, it is expected that most of the AB2 type Laves phase compounds of the ‘f’ electron systems may undergo the structural sequence: MgCu2 – MgZn2 (or MgNi2) – MgCu2 due to increased delocalization of their ‘f’ electron states.