A comparison of finite basis set and finite difference Hartree-Fock calculations for the open shell (Chi(2)Sigma(+)), species BeF, BO, CN and N-2(+)

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 algeb raic approximation) or finite difference methods in calculations employing the Hartree-Fock model for the open shell ground (X(2)Sigma(+)) states of t he 13-electron systems BeF, BO, CN and N-2(+). The convergence of the calcu lations carried out within the algebraic approximation is monitored by empl oying systematically constructed basis sets of increasing size. The accurac y of the finite difference calculations is assessed by employing two grids of different sizes, one of 32617 points and the other of 132385 points. The total Hartree-Fock energies supported by these two grids differ by less th an 0.05 mu E-h. The average difference between the finite basis set and fin ite difference Hartree-Fock energies is 1.3 mu E-h. Dipole moments determin ed within the algebraic approximation are compared with the corresponding f inite difference expectation values for the neutral species.