Perturbed Hartree—Fock Calculations. I. Magnetic Susceptibility and Shielding in the LiH Molecule

TLDR

The study applies a perturbed Hartree–Fock formulation to compute electric polarizability, magnetic susceptibility, and magnetic shielding, while examining how limited basis sets affect gauge invariance of magnetic properties. The authors solve the limited‑basis Hartree–Fock problem with a perturbation term to obtain a first‑order perturbed wavefunction and use two wavefunctions to calculate magnetic susceptibility, shielding, rotational magnetic moment, and spin rotational constants for LiH. Calculated magnetic susceptibility, shielding, rotational magnetic moment, and spin rotational constants for LiH agree reasonably with experiment for the latter two, and further refinement would alter results by only a few percent.

Abstract

The limited basis set Hartree—Fock problem is solved in the presence of a perturbation term in the Hamiltonian to obtain the first-order perturbed wavefunction. The formulation is applied to the calculation of electric polarizability, magnetic susceptibility, and magnetic shielding. The effect of the limited basis set on the gauge invariance of the magnetic quantities is discussed. The magnetic susceptibility and shielding, the rotational magnetic moment, and the spin rotational constants are calculated for lithium hydride using two different wavefunctions. The agreement with experiment is reasonably good for the spin rotational constants and rotational magnetic moment. It is felt that further refinement of the calculation would not change the results by more than a few percent.