High-Pressure Elastic, Vibrational and Structural Study of Monazite-Type GdPO4 from Ab Initio Simulations

Abstract

The GdPO 4 monazite-type has been studied under high pressure by first principles calculations in the framework of density functional theory. This study focuses on the structural, dynamical, and elastic properties of this material. Information about the structure and its evolution under pressure, the equation of state, and its compressibility are reported. The evolution of the Raman and Infrared frequencies, as well as their pressure coefficients are also presented. Finally, the study of the elastic constants provides information related with the elastic and mechanical properties of this compound. From our results, we conclude that monazite-type GdPO 4 becomes mechanically unstable at 54 GPa; no evidence of soft phonons has been found up to this pressure at the zone center.

Synthesis, Characterization, and Stability of Americium Phosphate, AmPO4

“…Whereas the peak positions stay essentially constant over time, within the ±1 cm –1 instrumental uncertainty, the fwhm varies significantly for some peaks. The former observation means that the A g vibrational lines are characterized by a very small (or vanishing) Grueneisen parameter, which is in reasonable agreement with the data reported in Munoz and Rodriguez–Hernandez . Our results differ from those for monazites irradiated by Au ions which showed that the A g band at 970 cm –1 exhibits an increase of the fwhm of approximately 30 cm –1 and a downshift in the peak energy of approximately 20 cm –1 for a radiation damage of the order of 0.04 dpa (corresponding to a fluence of 4 × 10 13 Au ions cm –2 ).…”

Electronic properties and high-pressure behavior of wolframite-type CoWO4

“…Although increasing with pressure, the Poisson ratio has a value <0.5 across the studied pressure range (Figure S5d), thus reflecting both the slightly anisotropic compressibility of wolframite-type CoWO 4 (see results in the XRD section) and an increasing ionic character of the chemical bond. 59,60 Finally, the bulk/shear ratio also increases under compression, indicating the high ductility of CoWO 4 (Figure S5d).…”

Experimental and Theoretical Study of SbPO4 under Compression

“…High-pressure (HP) studies of several A PO 4 orthophosphates have been reported in the literature; i.e., where zircon- and monazite-type phosphates have been broadly studied. − The pressure-induced structural sequence has been understood, with several new HP phases discovered and their crystal structures solved. In addition, the influence of pressure in the vibrational properties and unit-cell parameters has been well established.…”