Non-empirical calculations on diatomic transition metals. I. An investigation of various orbital contraction schemes of gaussian basis sets on the SCF level for Zn2

Ab initio SCF LCAO MO calculations with various contracted primitive gaussian basis sets were performed using Zn₂ as an example. When improving the basis set, polarization functions are shown to be more important for a proper reproduction of the repulsive potential curve, than a complete relaxation of the orbital contraction. This is considered to be true for all diatomics although for Zn₂ at larger internuclear distances no varr der Waals minimum is obtained on the SCF level.