Optimum atomic orbital exponents for molecular wave functions

Valence bond calculations have been made on the ground states of BH, CH+, NH and HF at several internuclear distances. The VB functions are constructed from a minimum basis of Slater-type atomic orbitals whose exponents are optimized at each internuclear distance. For calculations at the equilibrium distances on these molecules together with H2 and LiH, a good linear correlation has been found between the hydrogen exponent and the Mulliken population number. The importance of optimizing exponents at all internuclear distances is shown by comparing the potential energy curves obtained from fully optimized exponents with those obtained using best-atom or best-equilibrium-molecule exponents at all distances.