Absolute total energy of small copper clusters in an all-electron mixed-basis approach with the generalized-gradient approximation

In order to investigate the absolute value for the total and exchange-correlation energies of small transition metal clusters, an all-electron mixed-basis approach with the generalized gradient approximation (Perdew-Wang's GGA-1) is applied for the first time to small Cu clusters. We find that the GGA significantly deepens (2.57-2.59 a.u. per atom) both the total and exchange-correlation energies obtained with the local density approximation. A better agreement is obtained with experiments for the binding energy of Cu₂ when the spin-dependent calculation is used for an isolated Cu atom.