Electronic and magnetic structures and bonding properties of Ce2CrN3 and U2CrN3 from first principles

TL;DR

This study uses first-principles calculations to analyze the electronic, magnetic, and bonding properties of Ce2CrN3 and U2CrN3, revealing differences in their electronic structures, hardness, and magnetic moments, and classifying them as covalent nitrides.

Contribution

First-principles analysis of Ce2CrN3 and U2CrN3 provides new insights into their electronic, magnetic, and bonding characteristics, highlighting differences due to the nf elements.

Findings

U2CrN3 is harder than Ce2CrN3 due to smaller volume and less compressibility.

Ce2CrN3 exhibits large Cr magnetization and small Ce moment, indicating intermediate valence.

Both compounds are ferromagnetic in the ground state.

Abstract

The electronic and magnetic structures of A2CrN3 (A = Ce, U) ternary compounds calculated based on band magnetism within DFT exhibit different behaviors of the nf elements (n = 4, 5 resp.). Charge analysis allows to formally express the two compounds as A2Cr 5+ N3 5- thus classifying them as covalent nitrides, i.e. far from formal exchange of +- 9 electrons. From establishing the energy-volume equations of state, the two compounds are found with hardness magnitudes: B0(A=Ce) =192 GPa and B0(A=U) = 243 GPa, within range of oxides due to covalent metal-nitrogen bonding shown as based on overlap matrix analysis. The uranium compound is harder due to a smaller volume and less compressible U versus Ce metals. Ce2CrN3 exhibits large magnetization on Cr (1.94BM) and a very small moment develops on cerium (0.14 BM) pointing out to an intermediate valence state while in U2CrN3, M(Cr) = 0.49 BM and M(U) = 0.97BM. These results are stressed by broad band-like density of states (DOS) behavior for A=U and localized DOS for A=Ce. Both compounds are found ferromagnetic in the ground state