Theoretical and Experimental Studies on Gadolinium at Ultra High Pressure.

Abstract

The high-pressure structural phase transformations in gadolinium (Gd) were studied by energy-dispersive x-ray diffraction up to 118 GPa at room temperature using a synchrotron source. Gadolinium undergoes five transitions: h. c. p→Smtype→double-h. c. p→f. c. c→distorted f. c. c→b. c. m (body-centered monoclinic), with increasing pressures. The last transition to b. c. m occurs at 59±2 GPa, accompanied by a volume collapse of about 5%. We suggest that this low-symmetry structure and volume collapse in gadolinium is analogous to the well-known electronic transition in cerium metal related to loss of magnetic moment and eventual delocalization of f-shell under pressure.