Development of the exact exchange scheme using a basis set framework

A combination of the exact exchange (EXX) scheme for the approximation of the exchange term within the density functional theory is presented. For this task we have developed it and implemented in the atom code program. As will be discussed in this article, the use of this approach has the advantages of using a simple, but efficient, calculation numerical code and the refinement of. the EXX method for the exchange part within the Khon-Sham formalism. We present the development of the EXX theory within an atomic scheme for energy calculations. Results for several atomic systems are presented. We found a remarkable improvement in the energies of all the systems studied compared with the local density approximation and generalized gradient approximation approaches. (C) 2002 Wiley Periodicals, Inc.