Electronic Structure of Metal and Mixed Nonstoichiometric Clusters

Structural properties of nanoclusters: Energetic, thermodynamic, and kinetic effects

“…At N = 18 the most stable isomer was the double Ih minus one vertex, and at N = 20 the isomers based on pentagonal symmetries (which are closely related to the double Ih) were found to be more stable than structures with T d symmetry. On the other hand, Bonacić-Koutecký et al (1991) found that two T d structures are the lowest in energy for Li 20 and Na 20 (Bonacić-Koutecký et al, 1993b). Spiegelman et al (1998) found results in reasonable agreement with the previous calculations by a tight-binding approach.…”

“…As in the case of Au, the energetics of Ag clusters has been the subject of intensive study in all size ranges. For N ≤ 9, Bonacić-Koutecký et al (1993a searched for the lowest energy clusters by a self-consistent Hartree-Fock procedure which was able to produce structures in good agreement with the experiments (Alameddin et al, 1992;Ganteför et al, 1990;Ho et al, 1990;Jackschath et al, 1992). They found that the best isomers are planar up to the pentamer, as confirmed by Matulis et al (2003) by density-functional calculations.…”

“…Bravo-Pérez et al (1999b) correlated the preference for planar structures in Au to the fact that non-additive many-body interactions are stronger than additive 2-body ones in this element. Bonacić-Koutecký et al (2002) noticed that in planar Au clusters, d electrons contribute more to the bonding than in 3D structures; this would also qualitatively explain the weaker tendency to planar clusters for Ag, because in Ag the bonding is more of s type. Finally, Häkkinen et al (2002) investigated Au The tendency to form strained structures like icosahedra and decahedra, leading to large crossover sizes, and the tendency to present low-symmetry structures at geometric magic numbers have been discussed, in the framework of the same well defined and quite reliable energetic model, by Baletto et al (2002b) and Soler et al (2000).…”

“…Bonacić-Koutecký et al (1991) gave an excellent account of the earlier developments, which are very briefly summarized here. Systematic ab initio configuration-interaction studies on Li and Na clusters (Bonacić-Koutecký et al, 1988;Boustani et al, 1987) for N ≤ 9 have shown the complete analogy between the two elements. The lowest isomers are planar up to the pentamer; at N = 6 a pentagonal pyramid and a triangular planar structure are in very close competition; larger clusters are 3D.…”

“…This approach has allowed global minimum searches for N up to 100 atoms (Doye and Wales, 1998b;Erkoç and Yilmaz, 1999), and the comparison of selected magic structures belonging to the Ih, Dh and TO motifs for N up to 40000 atoms (Baletto et al, 2002b). Doye and Wales (1998b) modelled Ag by the Sutton and Chen (1990) potential and optimized Ag clusters at N ≤ 80, finding the same lowest energy structures as Bonacić-Koutecký et al (1993a) at N = 7, 8, 9, and Ih global minima at N = 13 and 55. 30 of the global minima were Ih in character, but several Dh and fcc clusters were found, the most stable being at N = 38 (TO) and N = 71, 75 (Dh).…”