A comparison of finite basis set and finite difference Hartree-Fock calculations for the BF, AlF and GaF molecules

Abstract

A comparison is made of the accuracy with which the total electronic energy can be calculated by using either the finite basis set approach (the algebraic approximation) or finite difference methods in calculations using the Hartree-Fock model for the ground (X¹Σ⁺) states of the Group IIIb fluorides: boron fluoride, aluminium fluoride and gallium fluoride molecules. The XF molecules, X = B, Al, Ga, are considered as a prototype for systems containing increasingly heavy atoms and numbers of electrons. The convergence of the calculations carried out within the algebraic approximation is monitored by employing systematically constructed basis sets of increasing size. The dependence of the finite difference calculations on the numerical grid employed is studied and it is found to be necessary to employ a multiple grid for the heaviest system, GaF, in order to achieve the target accuracy of 1 μE _h for the total energy.