Effect of chemical and external pressure on the structure of intermetallic compound CeNi

Neutron powder diffraction was employed to study the structural modifications of the intermediate-valence compound CeNi at room temperature induced by either chemical or external pressure. For the first time we were able to record the diffraction pattern resulting from the pressure-induced first-order phase transition occurring in CeNi at 300 K. At pressure P = 2 GPa we observe the coexistence of two phases while only single pressure-induced phase is visible at P = 5 GPa. The results obtained are indicative of a higher symmetry of the collapsed structure as compared to the CrB-type ambient pressure structure of CeNi. The critical pressure range around 2 GPa is found to be agreement with the previous estimation derived from the thermopower measurements.