MODELING OF NUMERICAL ATOMIC ELECTRON-DENSITY DATA WITH ANALYTICAL FUNCTIONS

An approach is presented for developing analytical models of user-defined atomic electron-density data. In place of tabulated data, modified Slater-type wavefunctions are used to describe ions and atoms. The desired charge distribution is obtained by adjusting orbital exponents, with orbital coefficients kept fixed to help maintain normalized functions. The analytical functions obtained by the fitting procedure are identical in form to standard Hartree-Fock wavefunctions, permitting the model functions to serve as input for Gordon-Kim electron gas calculations. For such work, Slater-orbital wavefunctions are used to calculate the electrostatic potential and electron density of ions in solids. The modeling procedure permits one to modify the character of an ionic charge cloud without resorting to numerical data. The approach is illustrated for the O2- ion; analytical functions are derived on the basis of a number of treatments: the standard closed-shell ion, a 'hybridized'' valence state, and empirical data.