ATOMS EMBEDDED IN AN ELECTRON-GAS - THE GENERALIZED GRADIENT APPROXIMATION

The bonding properties of atoms are studied within the atom-in-jellium model. The emphasis is on a comparison between the widely used local- density approximation (LDA) and the generalized-gradient approximation (GGA-PW91) for the electron exchange and correlation interactions. Th e analysis shows that the GGA is more able to account for energy diffe rences due to changes in electron density gradients (in mainly the val ence shells), as the free atom is immersed into an electron gas, than the LDA. GGA lowers the energies for free atoms and thus reduces the o verbinding present in LDA. Results are presented for a large fraction of the periodic system. The present work provide GGA basic parameters for the effective-medium theory (EMT), which is a glue-scheme method v ersatile for large systems of interacting atoms, and additional positi ve tests of the usefulness of GGA in density-functional calculations, showing it to pave the way towards chemical accuracy.