Effective Coulomb interaction in actinides from linear response approach

TL;DR

This paper calculates the effective Coulomb interaction (U) in actinide metals using a linear response approach within DFT, revealing how U varies across the series and improves the accuracy of structural and electronic property predictions.

Contribution

It introduces a method to compute U from linear response that is largely independent of exchange-correlation functionals and demonstrates its effectiveness in modeling actinide metals.

Findings

U varies systematically across the actinide series.

DFT+U with calculated U improves agreement with experimental lattice parameters.

The approach accurately reproduces bulk moduli and electron localization transitions.

Abstract

The effective on-site Coulomb interaction (Hubbard $U$) between 5$f$ electrons in actinide metals (Th-Cf) is calculated with the framework of density-functional theory (DFT) using linear response approach. The $U$ values seldom rely on the exchange-correlation functional, spin-orbital coupling, and magnetic states, but depend on the lattice volume and actinide element. Along the actinide series, the Coulomb parameter $U$ of $\alpha$-phase first decreases slowly, followed by a jump in the vicinity of Pu and then a monotonous increase. For light actinides, the lattice volume has a sizeable influence on $U$ while the localization of 5$f$ electrons is almost constant. But for transplutonium metals, $U$ is almost independent of the lattice volume but the electronic localization increases rapidly. The calculated lattice parameters from DFT+$U$ with the Coulomb parameters as input are in better agreement with the experimental values than those from DFT within local density approximation or Perdew-Burke-Ernzerhof approximation for solids (PBEsol). In particular, the agreement between PBEsol+$U$ and experiment is remarkable. We show that PBEsol+$U$ also well reproduce the experimental bulk moduli and the transition from itinerancy to localization of 5$f$ electrons along the series. Therefore it is concluded that DFT+$U$ with $U$ calculated from linear response approach is suitable for a good description of actinide metals.