APPLICATIONS OF ENGEL AND VOSKO GENERALIZED GRADIENT APPROXIMATION IN SOLIDS

Recently, Engel and Vosko have proposed an alternative form of a generalized gradient approximation (GGA) [Phys. Rev. B 47, 13 164 (1993)] within density-functional theory. This version of the GGA (EV93) was obtained by optimizing the exchange-correlation potential V-xc instead of the corresponding energy E(xc). We have applied this functional to various solids and found that equilibrium lattice constants generally are far too large in comparison to experiment, so that the total-energy aspect is unsatisfactory. However, EV93 describes FeO and CoO as antiferromagnetic insulators, while the local-spin-density approximation or the Perdew-Wang version of the GGA yields a metallic ground state. EV93 favors magnetism, e.g., the spin susceptibility of V is increased, but Pd remains nonmagnetic in agreement with experiment.