DENSITY-FUNCTIONAL APPROACH TO LCAO METHODS

A Kohn-Sham approach is presented for analyzing the many-body properti es of LCAO Hamiltonians. The total electronic energy of the system is shown to be a function of the different orbit al occupancies. Then an exchange-correlation potential is introduced for each orbital, taking into account extra-atomic and intra-atomic many-body effects. Using th is potential, the total energy can be obtained by calculating self-con sistently the orbital occupancies, avoiding the use of a local represe ntation as is done in the conventional LDA calculations. The method is applied to the calculation of the chemisorption energy and the charge transfer for the deposition of Na on Al(100), and the interaction of H with the GaAs(110) surface. Hydrogen is shown to passivate GaAs(110) surfaces for a monolayer deposition.