A COMPARISON OF FINITE BASIS-SET AND FINITE-DIFFERENCE HARTREE-FOCK CALCULATIONS FOR THE BF, ALF AND GAF MOLECULES

A comparison is made of the accuracy with which the total electronic e nergy can be calculated by using either the finite basis set approach (the algebraic approximation) or finite difference methods in calculat ions using the Hartree-Fock model for the ground (X(1) Sigma(+)) state s of the Group IIIb fluorides: boron fluoride, aluminium fluoride and gallium fluoride molecules. The XF molecules, X = B, Al, Ga, are consi dered as a prototype for systems containing increasingly heavy atoms a nd numbers of electrons. The convergence of the calculations carried o ut within the algebraic approximation is monitored by employing system atically constructed basis sets of increasing size. The dependence of the finite difference calculations on the numerical grid employed is s tudied and it is found to be necessary to employ a multiple grid for t he heaviest system, GaF, in order to achieve the target accuracy of 1 mu E(h) for the total energy.