DENSITY FUNCTIONALS FOR EXCHANGE AND CORRELATION ENERGIES - EXACT CONDITIONS AND COMPARISON OF APPROXIMATIONS

A set of exact conditions is compiled for the purpose of developing and testing approximations for the exchange-correlation energy as a functional of the electron density. Special emphasis is placed upon recently developed density-scaling relationships. Commonly used generalized gradient approximations are compared against several of these conditions. A direct tabular comparison of these functionals (not of calculated properties) with one another is also made. (C) 1994 John Wiley & Sons, Inc.