The structural response of gadolinium phosphate to pressure

A high-pressure single crystal diffraction study of GdPO4 with the monazite structure is presented. The elastic behaviour of rare-earth phosphates are believed to be sensitive to shear forces. The bulk modulus of GdPO4 measured under hydrostatic conditions is 128.1(8) GPa. Compression of the structure is facilitated by bending/twisting of the Gd−O−P links that result in increased distortion in the GdO9 polyhedra.162