Self-consistent molecular Hartree-Fock-Slater calculations - II. The effect of exchange scaling in some small molecules

The effect of varying the scaling parameter alpha in the X alpha exchange expression has been studied in a number of SCF LCAO MO Hattree-rock-Slater calculations an the diatomic molecules CO. NO, N-2, O-2, LiF and the hydrocarbon C2H4. The calculated ionization potentials and charge distribution of these molecules are in excellent agreement with experiment for alpha similar or equal to 0.70. From a comparison with results of the multiple scattering technique (MSX alpha), it appears that removing the muffin-tin approximations considerably improves the results or Hattree-Fock-Slater calculations.