DIRECT APPROACH TO DENSITY-FUNCTIONAL THEORY - HEAVISIDE-FERMI LEVEL OPERATOR USING A PSEUDOPOTENTIAL TREATMENT

A new method is presented for calculating electron densities in nonper iodic, polyatomic systems using Cartesian coordinates in three dimensi ons. The method blends a direct approach to spin-density-functional th eory and uses (1) the ''Heaviside-Fermi level operator'' h(E(F) - (H) over cap) rather than solving Schrodinger eigenvalue problems, (2) the distributed approximating functional for discretization and interpola tion, (3) a multigrid iteration procedure for accelerating the converg ence, (4) a separable, nonlocal form of pseudopotential, and (5) a fas t method for solving Poisson's equation in nonperiodic systems. Exampl e calculations of the electronic structure for the Ne atom and the C-2 and O-2 dimers are presented.