Hartree-Fock orbitals which obey the nuclear cusp condition

Recently we have constructed a self-consistent field program which uses Slater-type orbital (STO) basis sets. Here, we show how to amend the program so that orbitals are obtained that exactly satisfy the nuclear cusp conditions. Example calculations are presented, and in particular the question of the choice of appropriate STO basis functions is addressed. We examine variational Monte Carlo and the behaviour of the local energy using nuclear cusp-obeying orbitals. We also investigate properties which require the value of the wavefunction at the nucleus; in particular the Fermi contact term is examined.