An ab initio diatomic molecular integral program and some calculations on NiO.

A computer program for the calculation of molecular orbital self-consistent field (MO-SCF) eigenvalues and eigenvectors of diatomic molecules using the expansion method of Roothaan with Slater-type basis functions is presented. A copy of the program on 105mm microfiche is included in this volume; a listing of the program together with data and program formats and the mode of loading on a modern computer is given in a separate volume. Following a brief discussion of some aspects of Hartree-Fock (HF) theory a conventional SCF program employing the Roothaan Bagus and Jacobi diagonalization procedures is described in Chapter II ; the program employs the Restricted HF open- and closed-shell and the spin-polarized HF formalism. A unified treatment of the one- and two-electron integrals allows their efficient calculation and is the subject of Chapter III; numerical considerations and test values for the required integrals are given in Chapter IV. Chapter V describes the program developed for the formation of the two-electron 'supermatrices'. Minimal basis set test calculations on the ground state and a [3]pi(5o[1]2pi[1]) first excited state of the CO molecule at the experimentally determined equilibrium internuclear distances and suggestions for the improvement and extension of the program are given in Chapter VI. Preliminary calculations on diatomic Ni[2+]0[=] at an internuclear distance of 3. 938 a. u. are reported; the difficulties experienced in obtaining converged solutions with the trial vectors employed are discussed