APPLICATIONS OF SPECTRAL-REPRESENTATION MODEL AS A POTENTIAL METHOD FOR CU CLUSTERS

We applied the spectral-representation technique developed by Katsuki and Huzinaga as a model potential in calculating the electronic struct ure of Cu clusters. The characteristics of this potential were closely investigated in Cu and Cu-2. For Cu, Cu-2, Cu-5, Cu-9, and Cu-13, we performed all-electron ab initio self-consistent field calculations an d model-potential calculations where 3p, 3d, and 4s electrons, and 3d and 4s electrons are treated as valence electrons. The ionization pote ntials (IPs) given by the all-electron calculations were 6.26, 5.55, 4 .52, 4.02, and 4.08 eV for Cu, Cu-2, Cu-5, Cu-9, and Cu-13, respective ly. The IPs given by the model-potential calculations were 6.25, 5.56, 4.62, 4.09, and 4.23 eV for the 3p-, 3d-, and 4s-valence electrons, a nd 6.26, 5.68, 4.71, 4.07, and 4.19 eV for the 3d- and 4s-valence elec trons. The IPs given by the model-potential calculations agree well wi th those of the all-electron calculations. We also performed model-pot ential calculations where only the 4s electrons were treated as valenc e electrons. The calculated IPs were 6.47, 5.98, 5.38, 4.63, and 4.88 eV for Cu, Cu-2, Cu-5, Cu-9, and Cu-13, respectively. These are ca. 0. 8 eV higher than the IPs by the all-electron calculation for the large r clusters of Cu-5, Cu-9, and Cu-13. The higher IPs originate from the expulsion of the 3d electrons from the valence electrons. We also per formed model-potential calculations with 4s electrons for Cu-74. The c alculated IP is 4.61 eV, which is estimated to be 0.8 eV larger than t hat obtained by the all-electron calculation. The IPs with correlation corrections are 7.7, 7.4, 6.3, 5.8, 5.9, and 5.6 eV for Cu, Cu-2, Cu- 5, Cu-9, Cu-13, and CU74, respectively. Experimental values are 7.73, 7.37, 6.30, 5.37, 5.67, and 5.26 eV. The agreement between the two is fairly good. The electron affinities are also discussed. (C) 1996 by J ohn Wiley & Sons, Inc.