Zircon to monazite phase transition in CeVO4

TL;DR

This study investigates the pressure-induced zircon to monazite phase transition in CeVO4 using experimental techniques and theoretical calculations, revealing unique transition behavior and mechanical instabilities.

Contribution

It provides the first detailed experimental and theoretical analysis of the zircon to monazite transition in CeVO4, highlighting its distinctive features among rare-earth orthovanadates.

Findings

Transition occurs at 5.3 GPa with irreversible structural change.

Softening of specific vibrational modes indicates mechanical instability.

Theoretical calculations support experimental observations.

Abstract

X-ray diffraction and Raman-scattering measurements on cerium vanadate have been performed up to 12 and 16 GPa, respectively. Experiments reveal that at 5.3 GPa the onset of a pressure-induced irreversible phase transition from the zircon to the monazite structure. Beyond this pressure, diffraction peaks and Raman-active modes of the monazite phase are measured. The zircon to monazite transition in CeVO4 is distinctive among the other rare-earth orthovanadates. We also observed softening of external translational Eg and internal B2g bending modes. We attributed it to mechanical instabilities of zircon phase against the pressure-induced distortion. We additionally report lattice-dynamical and total-energy calculations which are in agreement with the experimental results. Finally, the effect of non-hydrostatic stresses on the structural sequence is studied and the equations of state of different phases are reported.