  Using the semiclassical neutral atom theory, we extend to fourth order the
modified gradient expansion of the exchange energy of density functional
theory. This expansion can be applied both to large atoms and solid-state
problems. Moreover, we show that it can be employed to construct a simple and
non-empirical generalized gradient approximation (GGA) exchange-correlation
functional competitive with state-of-the-art GGAs for solids, but also
reasonably accurate for large atoms and ordinary chemistry.

Other Condensed Matter;Materials Science;Chemical Physics