Electric quadrupole and hexadecapole moment, dipole polarizability and hyperpolarizability of the copper tetramer (Cu4) from pseudopotential calculations and a comparison with all-electron ab initio results

► Electric properties of clusters, electric moments polarizabilities and hyperpolarizabilities. ► Pseudopotential calculations have been performed on the rhombic copper tetramer. ► Comparison to all-electron ab initio and density functional theory calculations reveal discrepancies. ► The discrepancies are of increasing importance for hyperpolarizabilities.