A comparison of finite basis set and finite difference Hartree-Fock calculations for the open- shell (X2Σ+) molecules BeF,MgF, CaF and SrF

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 employing the restricted Hartree-Fock model for the open-shell ground (X²Σ+) states of the Group Ha fluorides BeF, MgF, CaF and SrF. The convergence of the calculations carried out within the algebraic approximation is monitored by employing systematically constructed basis sets of increasing size. By using two different grids, the accuracy of the finite difference calculations has been estimated to be of the order of 10^?2 μE _h. The average difference between the finite basis set and finite difference total Hartree-Fock energies is 2.75 μE_h. Dipole moments determined within the algebraic approximation are also compared with the corresponding finite difference expectation values.