United-Atom Approximation Applied to Argonlike Molecules. III. HCl and SiH4

Abstract

The united‐atom approximation has been used to obtain molecular wavefunctions for HCl and SiH₄ in the gaseous state. Theoretical values were determined, in each instance, for the molecular energy, bond length, force constant, molar diamagnetic susceptibility, and the coherent x‐ray scattering factor. Where possible, the results were compared with the corresponding experimental data. For SiH₄, a comparison of the present results was made with the earlier work of Carter and also of Albasiny and Cooper. These workers used, respectively, a numerical Hartree self‐consistent‐field approach and a numerical Hartree—Fock scheme, the latter study being performed within a spherical and a nonspherical approximation. For the HCl molecule, some comparison is made with the two‐center SCF—LCAO—MO calculation performed by Nesbet. In each case, the united‐atom treatment gave a molecular energy which was 98.9% of the experimental value. Other physical properties for HCl and SiH₄ derived from the present model compare favorably with similar quantities obtained from the more elaborate calculations and also with the corresponding available experimental data.