Icosahedral growth

Kumar, V., and Kawazoe, Y. 2002. Icosahedral growth, magnetic behavior, and adsorbate-induced metal-nonmetal transition in palladium clusters. Phys. Rev. B 66 144413. 

Magic numbers in spectra of calcium and strontium clusters also indicate icosahedral growth, while aluminium clusters appear to adopt an fee structure with octahedral morphology. Magic numbers observed when metal atoms are grown around a cluster... 

Mass spectra of transition metal clusters do not exhibit any abvmdance anomalies. However, if they are mixed with reactive gases prior to expansion into vacuum, the number of molecules being absorbed exhibits pronovmced size effects. Mass spectra may directly reveal the number of reactive sites on the cluster surface Coj, for example, offers six highly reactive sites towards ammonia. This number tends to increase with cluster size, but local minima are observed at certain cluster sizes, indicating closed shells or subshells in agreement with an icosahedral growth sequence. 

A pecuhar sohd phase, which has been discovered not too long ago [172], is the quasi-crystalline phase. Quasi-crystals are characterized by a fivefold or icosahedral symmetry which is not of crystallographic type and therefore was assumed to be forbidden. In addition to dislocations which also exist in normal crystals, quasi-crystals show new types of defects called phasons. Computer simulations of the growth of quasicrystals [173] are still somewhat scarce, but an increasing number of quasi-crystalline details are studied by simulations, including dislocations and phasons, anomalous self-diffusion, and crack propagation [174,175]. 

Many of the magic number combinations observed in the CMS of inert gas atoms have been identified with stable structures having an icosahedral symmetry (Echt et al. 1981). The Mackay icosahedra series (Hoare 1979 Mackay 1962) exhibits completion of the first three solvation shells as = 13, 55, and 147, respectively, such that the completion of solvation shells at n = 13, 55, etc., can arise from structures with a cuboctahedron symmetry (Hoare 1979). However, theoretical studies indicate that the icosahedral structures are more stable than those with cuboctahedral symmetry (Hoare 1979). The theoretical studies of Farges et al. (1986) and Northby (1987) provide insight into the growth of icosahedral structures. 

Contrary to this chemical cluster growth is the formation of naked, ligand free clusters in a more physical sense. Considering the cluster growth in Fig. 8 and 9, it is to be recognized that both five-fold symmetry and hexagonal (hep) or cubic (ccp) structures are realized. While in smaller clusters the icosahedral and cuboctahedral symmetry are... 

Northby27 discussed in detail the foundations of the lattice-growth approach and applied it in determining the structures of clusters for which the atoms interact with each other via Lennard-Jones potentials. As core structures Northby used structures derived from an icosahedron. He argued that also for cluster sizes for which icosahedra cannot be constructed directly, the icosahedron forms an important structural motif. Based on a single icosahedron, there are various ways of adding additional atoms. One set of structures is formed by the MIC structures, i.e., multi-layer icosahedral structures. Here,... 

Kuznetsov, Y. G., Malkin, A. J., Lucas, R. W, and McPherson, A. 2000. Atomic force microscopy studies of icosahedral virus crystal growth. Colloids SurfB Biointerfaces 19, 333-346. 

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