Effect of generalized gradient corrections on lanthanide cohesive properties

Abstract

We have calculated ab initio, using a full-potential linear muffin-tin orbital method, the equilibrium volumes, the bulk moduli, and the generalized cohesive energies for the entire lanthanide series and barium. Two different approximations to the density functional (DF) were compared: the local (spin) density approximation in the Hedin–Lundqvist parameterization (LDA) and the recently developed Perdew–Wang generalized gradient corrected functional, called the generalized gradient approximation (GGA). We find that GGA corrects most of the overbonding tendency of LDA. An interesting consequence of this is that, for the early lanthanides, the LDA results appear to agree better with experimental results than do the GGA results. In this case, we conclude that the 4f states probably have a significant impact on the equilibrium volumes of the early lanthanides. Both for the bulk moduli and for the generalized cohesive energies, we find that GGA generally, in comparison to LDA, gives results in closer agreement with experiment over the entire lanthanide series.