Bonding between transition metal atoms. A b i n i t i o effective potential calculations of Cu2

Abstract

Valence Hartree–Fock calculations using an ab inito effective potential and a Gaussian basis set of triple zeta quality followed by extensive CI’s have been carried out for several states of the copper atom and for the ground state of diatomic copper. Correlation effects are determined to obtain a satisfactory agreement with experimental data for Cu₂(r_e = 2.25 vs 2.22 Å; ω_e = 265 vs 266 cm⁻¹; D_e = 15 550 vs 16 500 cm⁻¹). The most striking effect is the 0.1 Å shortening of the bond length induced by the d correlation energy. Important basis set superposition errors are shown to be possible (especially in all electron calculations) and the use of six Gaussian primitives for the d orbitals was required to avoid them.