MANY-BODY EFFECTS ON BANDWIDTHS IN IONIC, NOBLE-GAS, AND MOLECULAR-SOLIDS

Electron bandwidths in LiD, LiF, LiCl, solid C-60, MgO, KCl, Ar, and C aF2, evaluated in the local-density approximation (LDA) and Hedin's GW approximation, are noted. Bandwidths are underestimated by the LDA as compared to GW results or experiment. This is explained by exchange a nd correlation effects being strongest on atomic or molecular sites, w hich compresses bands, with the LDA overestimating such compression. I t is reasonable for compression to occur because states at the band ma xima have more nodes between atoms or molecules, so that they are more concentrated on such sites. [S0163-1829(98)03036-7].