X-ray absorption study on the origin of the deviation from Vegard's law for U(Al1−xGex)3 solid solution

Abstract

The cell parameter evolution along the cubic U(Al1−xGex)3 solid solution shows a significant deviation from Vegard's law. The origin of such deviation has been investigated by X-ray powder and electron diffractions, EXAFS and HERFD XANES at the U L3 and Ge K edges and specific heat measurements. The results of such investigations show that, from the structural point of view, U(Al1−xGex)3 does not present any local or long range ordering and the deviation from Vegard's law is caused by valence instability of U with an actual decrease of the U–Ge bond length with increasing Al-content and cell parameter.