On the large-gradient behavior of the density functional exchange energy

A coordinate-space model of the exchange hole density, previously introduced by the author, is extrapolated to the case of very strongly inhomogeneous systems (i.e., large density gradients). As a result, we propose a new gradient-corrected exchange energy functional for application to atomic and molecular problems. The model provides theoretical estimates of the parameters in the functional, and these compare well with empirical values deduced from a least squares fit to exact atomic data.