  The pressure-induced structural phase transition in the intermediate-valence
compound CeNi has been investigated by X-ray and neutron powder diffraction
techniques. For the first time it is shown that the structure of the
pressure-induced CeNi phase (phases) can be described in terms of the Pnma
space group. Equations of state for CeNi on both sides of the phase transition
are derived and an approximate P-T phase diagram is suggested for P < 8 GPa and
T < 300 K. The observed Cmcm -> Pnma structural transition is analyzed using
density functional theory (DFT) calculations, which successfully reproduce the
ground state volume, the phase transition pressure, and the volume collapse
associated with the phase transition.
