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

TL;DR

This study identifies the P6/mmm omega-phase as the true ground state of U2Mo, revealing its stability, elastic isotropy, and electronic hybridization characteristics through ab initio calculations.

Contribution

It proposes the omega-phase as the stable ground state of U2Mo, replacing the previously assumed structure, and characterizes its physical and electronic properties.

Findings

Omega-phase is stable and ductile

Material exhibits elastic isotropy

High hybridization between Mo and U electronic states

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.