Exchange and correlation in density functional theory

Abstract

The accurate description of exchange and correlation effects is a key issue in density functional theory (DFT). In spite of its widespread use, the local density approximation (LDA) has well-known deficiencies. In atoms, the empirical correlation energies are of the same magnitude as the errors of the LDA for exchange. This means that an accurate description of exchange in atoms or molecules is a prerequisite for the introduction of Coulomb correlation. One of the methods that today achieve such an accuracy is the weighted density approximation (WDA). Calculations of the exchange and total energies are presented to substantiate this statement. An optimized local-like approximation (OLA) to Coulomb correlation, based on an explicit modeling of the Coulomb hole, is then combined with the WDA for exchange. The results for total energies and other atomic properties look very promising. A combination of the OLA with several generalized gradient approximations (GGAS) for exchange is explored for molecules. © 1995 John Wiley & Sons, Inc.