Density functional theory study on the stability and electronic properties of Cu_n(n = 2∼20) clusters

The stability and electronic properties of Cu_n(n = 2∼20) clusters were studied by using the method of PW91/DNP in density functional theory. The results show that the average binding energy curve increases linearly with cluster size n = 2∼8, it becomes more flat versus cluster size n = 9∼20. Cu_n(n = 4, 7, 8, 17) clusters are more stable than the others. The energy gaps of Cu_n(n = 2, 4, 8, 13, 19) clusters are larger than the others, so their chemical activity is also weaker than the others. The vertical ionization energy is slightly greater than the adiabatic ionization energy and the adiabatic affinity energy is slightly greater than the vertical affinity energy between the cluster size n = 2∼20. The ionization energy curve shows a significant odd-even oscillation effect, namely the ionization energy of the cluster whose size is even number is larger than that of the near cluster whose size is odd number, and the affinity energy curve also shows a significant odd-even oscillation effect but which is opposite to that of the ionization energy curve. (authors)