SCF-MO Wave Functions for the Hydrogen Fluoride Molecule

Abstract

An SCF-LCAO-MO ground-state wave function is reported for the HF molecule at several internuclear distances. The basis set of Slater-type orbitals (STO's) was chosen so as to obey the following four criteria: (a) be a balanced basis set, i.e., each atom should have a set of STO's equally extended relative to the number and kinds of occupied AO's in the free atom; (b) include in the set STO's for a balanced polarization; (c) optimize the orbital exponents; (d) avoid redundancy in the set. The computed total energy at the internuclear distances of 1.7328 a.u. is —100.05804 a.u. This should be about 0.004 a.u. above the Hartree-Fock energy of the HF molecule. The significance of the STO's in the basis set adopted is illustrated by several parallel computations. The computed equilibrium distance is 1.74 a.u. and the experimental is 1.733 a.u. The dipole moment is computed for several wave functions and the value corresponding to the best wave function is 1.984 D (experimental is 1.74 D), whereas the best computed moment for another wave function is 1.970 D. The significance of this variation is discussed. The dμ/dr is estimated at 1.7 D/a.u. at the equilibrium distance (experimental is 0.954). The overlap population and gross charge Q are computed for several internuclear distances. The significance of the QH is discussed; the best value of QH at the internuclear distance is 0.479. The ground-state 2Π and the excited-state 2Σ+ for HF are investigated. An SCF computation is made for the 2Π+ excited state at several internuclear distances. Gross charges and overlap populations are given for different internuclear distances for the two ionic states. The reorganization effect due to the removal of one electron is discussed in relation to the total energy, population analysis, and gross charge QH for the ion. A discussion of the computed ionization potential I(3σ) is given at the end of the paper.