Phase Transitions and Structural Stability of Binary Uranium Intermetallics Under High Pressure: A Review

The f-electron based intermetallic compounds (f-IMCs) have unique nature of the f-electrons which are tuned in a controlled manner by changing the interatomic distances by applying external or chemical pressure. Among the f-IMCs, uranium intermetallics (U-IMCs) hold a very special position because of their technological importance. In this paper the phase transitions and structural stability investigations under pressure on uranium binary intermetallics are reviewed. The importance of magnetism in U-IMCs is briefly discussed. Under pressure, the UX type (where X could be a transition metal or a chalcogen) compounds generally transform from B1 phase to B2 phase, whereas some of the UX2 compounds display series of structural transitions. UX3 compounds show large range of stability under pressure. Our own experiments and calculations on few typical uranium compounds are given as examples. Wherever needed, the electronic structure calculations are discussed and correlated to the observed behavior of the compounds under pressure. The importance and the relevance of the Hill plot are examined for uranium binaries. The need to build structural stability maps for predicting high pressure phases is emphasized.