Density functional study of the actinide nitrides

Abstract

The full-potential all-electron linearized augmented plane wave plus local orbital method, as implemented in the suite of the software WIEN2K, has been used to systematically investigate the structural, electronic, and magnetic properties of the actinide compounds AnN ($\mathrm{An}=\mathrm{Ac}$, Th, Pa, U, Np, Pu, and Am). The theoretical formalism used is the generalized gradient approximation to density functional theory with the Perdew-Burke-Ernzerhof exchange-correlation functional. Each compound has been studied at the nonmagnetic, ferromagnetic, antiferromagnetic configurations, all with and without spin-orbit coupling (SOC). The structural parameters, bulk moduli, densities of states, and charge distributions have been computed and compared to available experimental data and other theoretical calculations published in the literature. Our total energy calculations clearly indicate that AcN, ThN, and PaN are nonmagnetic, while the ground states of UN, NpN, PuN, and AmN are found to be ferromagnetic. The influence of SOC in the actinide nitrides is found to be significant. The nature of the interactions between the actinide metals and nitrogen atom and the implications on $5f$ electron delocalization and localization are discussed in detail.