Distributed Gaussian basis sets: a comparison with finite difference Hartree–Fock calculations for potential energy curves of H2, LiH and BH

Abstract

Within the Hartree–Fock approximation, distributed basis sets of s-type Gaussian functions are used to compute those portions of the ground-state potential energy curves of the H2, LiH and BH molecules for which the model is appropriate. The exponents are generated using the even-tempered prescription and an anharmonic model is employed to distribute the basis functions. For few-electron diatomic systems, this approach is known to support sub-μHartree accuracy for electronic energies. For the molecules studied in the present work, matrix Hartree–Fock energy expectation values are compared with finite difference Hartree–Fock calculations carried out at the same geometries and using grids designed to support an accuracy of at least 1 nanoHartree. The distributed basis sets developed in this work support matrix Hartree–Fock energies which differ from the corresponding finite difference energies by 0.41, 0.58 and 0.68 μHartree, respectively, for the ground states of the H2, LiH and BH molecules at their equilibrium geometries. For each of these systems, a sub-μHartree level of accuracy is supported for a range of geometries.