On the accuracy of the algebraic approximation in molecular electronic structure calculations. I. Calculations for H2+, HeH2+, H2 and HeH+ using basis sets of atom-centred Gaussian-type functions

Abstract

The accuracy of electronic structure calculations made within the algebraic approximation (that is by making finite basis set expansions) is compared with the results of previously reported fully numerical calculations for diatomic molecules. Sequences of even tempered basis sets of atom-centred Gaussian-type functions are employed to explore the accuracy that can be achieved in matrix calculations for the H2+, HeH+ and HeH2+ molecular ions and the H2 molecule. It is demonstrated that sub- mu Hartree accuracy can be achieved in energy calculations. The relevance of these results to the accuracy that can be achieved in studies of polyatomic studies is emphasised.