First-principles investigations of the electronic and magnetic structures and the bonding properties of uranium nitride fluoride (UNF)

Abstract

Abstract Based on geometry optimization and magnetic structure investigations within density functional theory, a unique uranium nitride fluoride, isoelectronic with UO2, is shown to present peculiar differentiated physical properties. These specificities versus the oxide are related to the mixed anionic substructure and the layered-like tetragonal structure characterized by covalent-like [U2N2]2+ motifs interlayered by ionic-like [F2]2− ones and illustrated herein with electron localization function projections. Particularly, the ionocovalent chemical picture shows, based on overlap population analyses, stronger U–N bonding versus U–F and d(U–N)<d(U–F) distances. Further generalized gradient approximation+U calculations provide the ground state magnetic structure as insulating antiferromagnet with ±2 μB magnetization per magnetic sub-cell and ~2 eV band gap.