Molecular symmetry. IV. The coupled perturbed Hartree–Fock method

✍ Scribed by Toshikazu Takada; Michel Dupuis; Harry F. King

• Publisher: John Wiley and Sons
• Year: 1983
• Tongue: English
• Weight: 526 KB
• Volume: 4
• Category: Article
• ISSN: 0192-8651
• DOI: 10.1002/jcc.540040214

✦ Synopsis

Symmetry methods employed in the ab initio polyatomic program HONDO are extended to the coupled perturbed Hartree-Fock (CPHF) formalism, a key step in the analytical computation of energy first derivatives for configuration interaction (CI) wavefunctions, and energy second derivatives for Hartree-Fock (HF) wavefunctions. One possible computational strategy is to construct Fock-like matrices for each nuclear coordinate in which the one-and two-electron integrals of the usual Fock matrix are replaced by the integral first derivatives. "Skeleton" matrices are constructed from the unique blocks of electron-repulsion integral derivatives. The correct matrices are generated by applying a symmetrization operator. The analysis is valid for many wavefunctions, including closed-or open-shell spin-restricted and spin-unrestricted HF wavefunctions. To illustrate the method, we compare the computer time required for setting up the coupled perturbed HF equations for eclipsed ethane using D 3 h symmetry point group and various subgroups of D3h. Computational times are roughly inversely proportional to the order of the point group.