Approximate Integral Evaluations Used in the Molecular Quantum Mechanics of Nonlinear Molecules

Publisher Website
Google Scholar
Abstract
Molecular energy calculations employing actual and approximate multicenter angular dependent integral evaluations are compared. Individual integral values for three‐center integrals used in calculations for the triangular H3+ ion as computed by exact methods and by the approximate formulas of Mulliken and of Rudenberg are given. The results indicate that angular and distance relations of the nuclear skeleton of this polyatomic ion are determinable at almost the identical ``best'' value found using the much more laborious exact integral calculations. The energies of the approximate evaluations, however, indicate that once these ``best'' parametric values are determined the more exact calculations must be used. The approximate evaluations of second angular derivatives of integrals that are dependent on the angular and distance relations of component molecular nuclei are also computed and compared. Use of such derivatives in determination of approximate zero point energies, vibrational frequencies, and force constants is indicated.

This publication has 15 references indexed in Scilit: