Pressure-induced structural phase transition in CeNi: X-ray and neutron scattering studies and first-principles calculations

Abstract

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 P nma 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 → P nma 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.

Dynamic magnetic response across the pressure-induced structural phase transition in CeNi

“…Note that the enhanced 4 f -3d hybridization after the transition follows also from our structural results and ab initio CeNi electronic structure calculations. 26 Therefore, similar to the case of metallic cerium, [4][5][6]9,10 the interaction between 4 f electrons of Ce and the conduction band electrons plays a key role in the mechanism of the volume-collapse structural transition in CeNi.…”

“…3). Therefore, the structural transition accompanied by volume jump (∆V /V ∼ 8% at low temperatures 26 ) results in the increase in characteristic energy scale of magnetic fluctuations (Kondo temperature) while their lifetime decreases,that is, fluctuations dissipate faster than at ambient pressure.…”

“…Recently, we performed detailed x-ray and neutron powder diffraction experiments to study this transition in CeNi and showed that the structure of the pressure-induced phase can be described in terms of the Pnma space group. 26 Equations of state of CeNi on both sides of the phase transition were derived and an approximate P-T phase diagram was suggested for P < 8 GPa and T < 300 K. The observed C mcm → Pnma structural transition was analyzed using density functional theory calculations, which successfully reproduced the ground state volume, the phase transition pressure, and the volume collapse associated with the phase transition. We concluded that the decrease of the Ce-Ni interatomic distances suggests an enhanced Ce 4 f -Ni 3d hybridization in the high-pressure CeNi phase as compared to the ambient pressure CeNi structure.…”