Pressure-induced amorphization mechanism in Eu(2)(MoO(4))(3)
Résumé
We identify a mechanism responsible for amorphization of rare-earth molybdate isostructural compounds by means of x-ray absorption spectroscopy (XAS) and Raman spectroscopy as well as first-principles calculations. Our present Raman spectra show that both beta' and alpha-Eu(2)(MoO(4))(3) undergo a pressure-induced amorphization. Both first-principles calculations and XAS measurements explain the process of amorphization by a spatial self-reorganization of the oxygen clouds around the Mo and Eu subnetworks as the pressure is increased inducing a change in the coordination number of the Mo atoms. This latter transforms the eg crystal field of the tetrahedra into a series of stabilization-degenerated peaks, which energetically favors a disordered overlapping of the former MoO(4) tetrahedra instead of a mere ordered compression and rotation of these fragments