ELECTRONIC-PROPERTIES OF F-ELECTRON METALS USING THE GENERALIZED GRADIENT APPROXIMATION

We present a comparison between calculations based upon the local-density approximation (LDA) and the generalized gradient approximation (GGA) of the ground-state properties of the f-electron metals Ce, Th, Pa, U, Np, and Pu in their alpha phase. For alpha-Ce, Th, Pa, U, and Np the calculations have been performed for the observed crystal structures. Studies for the hypothetical fee crystal structure have also been done for Pa, U, Np, and Pu. Equilibrium volumes and bulk moduli for these f-electron metals have been calculated for both the LDA and GGA formulation of the exchange-correlation energy functional in the full-potential implementation of the linear-muffin-tin-orbital method. The equilibrium volumes, which generally are too low in LDA calculations, are improved considerably by the gradient correction for these elements. Similarly the bulk moduli are decreased substantially when LDA is replaced by GGA and thereby they come closer to the experimentally observed values.