Basis set convergence towards the numerical limit of the total Hartree-Fock (HF) energy is investigated for the hierarchical sequences of the XZP and cc-pVXZ basis sets. For both hierarchies, solid improvements are obtained with each increment in X. To estimate the complete basis set limit, an exponential form was used. Among the various approaches considered here, a three-parameter exponential extrapolation applied to the TZP, QZP, and 5ZP results yields the most accurate basis set limits. In addition, 5ZP highest occupied molecular orbital HF energies of some diatomic molecules are evaluated and compared with the corresponding ones obtained with the cc-pV5Z and numerical HF results.
ab initio; calculations; diatomic molecules; Gaussian basis set; total and orbital HF energies
