The structural response of gadolinium phosphate to pressure

Abstract

Accurate elastic constants for gadolinium phosphate (GdPO 4) have been measured by singlecrystal high-pressure diffraction methods. The bulk modulus of GdPO 4 determined under hydrostatic conditions, 128.1(8) GPa (Kʹ = 5.8(2)), is markedly different from that obtained with GdPO 4 under non-hydrostatic conditions (160(2) GPa), which indicates the importance of shear stresses on the elastic response of this phosphate. High pressure Raman and diffraction analysis indicate that the PO 4 tetrahedra behave as rigid units in response to pressure and that contraction of the GdPO 4 structure is facilitated by bending/twisting of the Gd−O−P links that result in increased distortion in the GdO 9 polyhedra.

Indentation recovery in GdPO4 and observation of deformation twinning

“…2,4,13 High shear stresses underneath the indentation likely promote twinning, but GdPO 4 is quite sensitive to the presence of shear stresses even in high-pressure diamond anvil cell experiments. 14 Analysis of polycrystalline GdPO 4 in the un-deformed regions did not show twins or stacking faults, indicating that these defects arose during indentation testing. Given the observation of twins and stacking faults, a plausible explanation for the observed indentation recovery includes the following steps: (1) The material generates twins upon loading to accommodate strain, and further strain is partially relieved by the movement of twin boundaries.…”

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

“…Previous theoretical results [20] differ slightly due to the exchange-correlation functional used in the calculations. [18]. c Reference [11].…”

“…Therefore, the study of these orthophosphates under high pressure is very promising for future practical applications. Although there are several studies focused on pressure-induced transition and on the structural and vibrational properties of monazite phosphates under pressure [7,[14][15][16][17][18], these studies were carried out only up to 30 GPa. A systematic understanding of their properties has not yet been achieved; the study of their elastic and mechanical properties is scarce [5,19,20].…”

High‐pressure phase transitions and properties of MTO4 compounds with the monazite‐type structure

“…In particular, the compression of it accounts for most of the volume reduction of the monazite structure. However, the contraction of the unit‐cell volume is not only facilitated by the decrease of the volume of the MO 9 polyhedron, but also favored by the bending and twisting of the MOT links, which result in a pressure enhanced distortion in the MO 9 polyhedron .…”