Incommensurate-to-incommensurate phase transition in Eu metal at high pressures.

High pressure x-ray powder-diffraction experiments were performed on europium metal up to ~70 GPa. Above 38 GPa, europium transforms from the incommensurately modulated Eu-IV phase to a second phase with an incommensurately modulated crystal structure, Eu-V. This is a previously unseen incommensurately modulated to incommensurately modulated transition in the elements at high pressure. High-pressure high-temperature experiments were also performed up to 449 K in order to make an initial estimate of the positions of the phase boundaries of the incommensurate phases. [ABSTRACT FROM AUTHOR]