ON THE ACCURACY OF THE ALGEBRAIC-APPROXIMATION IN MOLECULAR ELECTRONIC-STRUCTURE CALCULATIONS .3. COMPARISON OF MATRIX HARTREE-FOCK AND NUMERICAL HARTREE-FOCK CALCULATIONS FOR THE GROUND-STATE OF THE NITROGEN MOLECULE

A comparison of matrix Hartree-Fock calculations using basis sets of Gaussian-type functions with numerical Hartree-Fock studies is made for the ground state of the nitrogen molecule. The use of both atom- and bond-centred functions is investigated. It is shown that by employing systematic sequences of even-tempered basis sets the accuracy achieved in the numerical Hartree-Fock calculations can be approached when basis sets of atom-centred functions are employed and can be matched when bond-centred functions are included. An energy of -108.993 823 Hartree is obtained within the algebraic approximation which should be compared with -108,993 808 Hartree and -108.9939 Hartree from previously reported fully numerical and semi-numerical calculations. The advantages of the matrix Hartree-Fock method are emphasized.