Ground state of the U2Mo compound: Physical properties of the Omega-phase

Abstract

Using ab initio calculations, unexpected structural instability was recently found in the ground state of the U$_2$Mo compound. Instead of the unstable $I4/mmm$ structure, in this work the $P6/mmm$ ($\# 191$) space group, usually called $\Omega$-phase, is proposed as the fundamental state. Electronic and elastic properties are studied in this work in order to characterize the physical properties of the new ground state. The stability of the $\Omega$-phase is studied by means of its elastic constants calculation and phonon dispersion spectrum. Analysis of isotropic indices shows that the new phase is a ductile material with a minimal degree of anisotropy, suggesting that U$_2$Mo in the $P6/mmm$ structure is an elastic isotropic material. Analysis of charge density, density of electronic states (DOS) and the character of the bands revealed a high level of hybridization between $d$-molybdenum electronic states and $d$- and $f$-uranium ones.