Noble gas clusters

Van der Waals clusters (N2) (C02) noble gas clusters Molecular clusters (L2)n clusters of organic molecules H-bonding clusters (H20) ... 

We shall therefore briefly review the experimental efforts in this field throughout the last century. Soon after Louis de Broglie proposed his wave hypothesis for material particles matter wave phenomena were experimentally verified for electrons [Davisson 1927], atoms and dimers [Estermann 1930], and neutrons [Halban 1936 Gahler 1991]. A replica of Young s double-slit experiment with matter waves was demonstrated by Jonsson for electrons [Jonsson 1974], by Zeilinger et al. for neutrons [Zeilinger 1988], by Carnal and Mlynek for atoms [Carnal 1991] and by Schollkopf and Toennies for small molecules and noble gas clusters [Schollkopf 1994 Schollkopf 1996 Bruch 2002],... 

Figure 15. Relative energies (kcal/mol) of the two methane cation - noble gas cluster models depicted in Fig. 14, as functions of distance between the noble gas atoms and the nearest atom(s) in CHJ. In the calculations, both the VWN and PP functionals are employed, keeping the PP/IGLO-III optimized geometry of CHJ (Fig. 14a) fixed throughout.

In Fig. 16 we depict the variation of the isotropic hf structures of CHJ as functions of varying distance to the noble gas cluster atoms (PP calculations only). For both systems, there is a dramatic change in the isotropic... 

Figure 16. The variations of the isotropic hf coupling constants of the CH atoms in the two noble gas clusters, as functions of the X - CHj distances. Only the PP calculations are shown. Solid lines Ne6 cluster dashed lines Ar6 cluster. Throughout, the PP/IGLO-III optimized vacuum geometry (Fig. 14a) is used, and held fixed. The labels for the Ne and Ar results are placed in the regions where the energy minima (Fig. 15) are observed.

The closed sub-shell electronic configuration, 6s, of the free Hg atom causes small mercury clusters to be non-metallic and held together by relatively weak van der Waals dispersion forces (as found, for example, in noble gas clusters). As the cluster grows, the atomic 6s and 6p levels broaden into electronic energy bands (Fig. 7). A metal-insulator transition within the cluster is presumed to occur at a critical nuclearity (Nc) because of 6s-6p band overlap (as shown in Fig. 7), al-... 

About 35 years ago, the production of noble-gas clusters and metallic clusters became available as a result of free beam sources [21, 22). Let us estimate the time scale of 1 run size nanocluster production by these techniques [23]. There, the typical metal vapor temperature, T, is about 1500 K and the pressure, p, is nearly equal to 500 Pa, and the estimated size of the clusters is L = 1 nm. Then, using the kinetic theory of gases, one obtains the incident atomic flux on the cluster, F, which is the number of metal atoms hitting the nanocluster surface per second ... 

The simplest weakly-bound clusters are those built from noble gas atoms, such as neon and argon. What do we expect to be the optimal structure for one of these noble gas clusters, and how does the structure depend on the cluster size For that matter, can we even describe these clusters in terms of just one structure ... 

In spite of its simplicity, the Lennard-Jones potential may not be used for accurate description of cluster properties with the possible exception of noble gas clusters. Often empirical potentials that involve a larger number of parameters than the two-parameter Lennard-Jones potential are employed for structural determination. 

Small noble gas clusters have been studied as a benchmark for GA optimization in those earlier studies. Zeiri has studied the lowest energy structures of very small Lennard-Jones clusters (n = 4-10) using GA and found that GA based method converges to the global minima much more rapidly than some other techniques. ... 

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