Cluster crystals

DJ Wales, HA Scheraga. Global optimization of clusters, crystals, and biomolecules. Science 285 1368-1372, 1999. 

Cluster Crystal structure Method of preparation Refs. 

These investigations are not yet finished. We hope that by starting with M55 clusters crystal growth can be observed step by step for the first time and possibly some of the unsolved problems and questions concerning crystal growth may be solved in the future. 

Figure 5.17 The two-dimensional layer in [(C6H5N02)2Ln(H20)4]2[IMo6024][N03] [59]. (Reprinted with permission from H.Y. An, et al., Self-assembly of extended high-dimensional architectures from Anderson-type polyoxometalate clusters, Crystal Growth and Design, 6, no. 5, 1107-1112 (Figure 3), 2006. 2006 American Chemical Society.)...

The distance between metal ion clusters and the orientation of the clusters in zeolite cages depends on the zeolite hosts, and as a result the three-dimensional arrays can be described in different ways. They can be called cluster crystals or superlattices. The Na/ Na-Y cluster crystal formed by accommodation of one Na43+ cluster in each sodalite cage is written as in Equation (9.2) ... 

Figure 9.6 Cluster crystals formed by Na43+ clusters located in the sodalite cages of zeolites with different structures, (a) Sodalite (SOD), (b) Zeolite Y (FAU). (c) Zeolite A (LTA). Although the array shown in (c) has not been prepared, the analogous potassium clusters shown in (d) is indeed available in (d) the cluster crystal is actually composed of K43+ clusters in all the sodalite cages and the larger K,24+ clusters in every other a-cages. Reproduced from [4], Copyright (2002) Springer-Verlag...

Fig. 9. Cross section of a bract from the fruiting plant a, cystolith hair A large grandular hair with several cells in head and stalk c, head of one of the large glandular hairs d, small glandular hair with bicellular head artd unicellular stalk e, thick walled conical trichomes f, large developing glandular hair i stalk of a large glandular hair h, palisade cell /, cluster crystal / parenchymal cell /r, stomata. (Reprinted by permission, from Joyce and Curry, The Botany and Chemistry of Cannabis, 1970. Drawn by D. Erasmus.)...

Clustering, crystallizing, dispersing In the delicate balance of radiation And the adiabatic lapse rate. 

Therefore the ratio of in a spectrum of an examined film to D )a in a spectrum of the same film annealed at 373 K characterizes a degree of the cluster crystallization (Table 2.1). Spectral data show that the position of plasmon band for nanocrystals in Ag-PPX films heated from 77 to 298 K shifts to the long-wavelength range and then does not change at heating from 298 to 373 K (Table 1). The same effect was observed for Ag-CIPPX films [24]. 

An alternative method of distinguishing between jute and kenaf is by means of the crystals in the ash of the fiber after incineration. These crystals are present in the parenchyma and retain their original form during asking. In kenaf, cluster crystals are commonly found in the ash, whereas they are relatively uncommon in the case of jute. Jarman and Kirby [18], however, have shown that jute can be distinguished by the fact that the ash contains solitary crystals occurring in chains. Solitary crystals may occur in kenaf, but not in chains. 

Enormous expansion has happened in the field of nanoclusters and researchers have shown an effective role of mass spectrometry in characterizing such pieces of matter. It is important to mention here that mass spectrometiy is not the only tool to characterize such clusters. Crystal structure is veiy much important to understand the detailed structure. Although there are plenty of reports of clusters assigned through mass spectrometry, only a few of them have been crystallized. A brief discussion of the clusters ctystallized is given in Table 1. In general, the structures consist of a metallic core which are surrounded by... 

The usual chemical and spectroscopic techniques such as elemental analyses, molecular weight determinations, and infrared, NMR, and electronic spectroscopy, are frequently useful for the characterization of transition metal cluster compounds. However, x-ray crystallography and, to a lesser extent, mass spectrometry, are almost indispensable for the unambiguous identification of new metal cluster systems. Indeed, much of the rapid progress in metal cluster chemistry since the appearance of Cotton s review article in 1965 (98) can be attributed to the widespread availability of automated x-ray-diffraction equipment. This increases significantly the number and accuracy of crystal structures that can be determined with a given amount of manpower, and thus the analyses of a great many more new metal cluster crystal structures are completed each year. 

Theoretical Chemical Physics encompasses a broad spectrum of Science, where scientists of different extractions and aims jointly place special emphasis on theoretical methods in chemistry and physics. The topics were gathered into eight areas, each addressing a different aspect of the field 1 - electronic structure of atoms and molecules (ESAM) 2 - atomic and molecular spectra and interactions with electromagnetic fields (AMSI) 3 - atomic and molecular interactions, collisions and reactions (AMIC) 4 - atomic and molecular complexes and clusters, crystals and polymers (AMCP) 5 - physi / chemi-sorption, solvent effects, homogeneous and heterogeneous catalyses (PCSE) 6 - chemical thermodynamics, statistical mechanics and kinetics, reaction mechanisms (CTRM) 7 -molecular materials (MM), and 8 - molecular biophysics (MB). There was also room for contributions on electrochemistry, photochemistry, and radiochemistry (EPRC), but very few were presented. 

For very small metallic particles, or clusters, crystal faces have no meaning. It is better to define surface structure with the notation introduced by Van Hardeveld and Hartog. They consider the coordination number i of a surface atom and the coordination number j of a surface active site, which was called as coordination model. Surface atom is denoted by Cj when it has i nearest neighbors. The active site is denoted by By when it has j nearest neighbors. Examples of C4, Ce and C7 atoms are shown in Fig. 2.8. Several active sites, B4, B5, Be and B7 are shown in Fig. 2.9. 

B.C. Bolding, H.C. Andersen, Interatomic potential for sUicon clusters, crystals, and surfaces. Phys. Rev. B 41, 10568-10585 (1990)... 

G.L., Fultz. W.C. and Rheingold. A.L. (1983) Interconversion of methylene and ketene ligands on a triosmium cluster. Crystal and molecular structure of the ketene complex Os3(CO)]2(t -(C.C). j-CH2CO). Journal of the American Chemical Society, 105,... 

More generally, one may wish to ensure that the choice of the soft, intersegment potential, v, results in a liquid state. The phase diagram of fluids of soft particles has been explored and exhibits quite a rich behavior [106-108]. In addition to the liquid and crystal phases that occure in fluids with harsh repulsions exhibit at low temperatures, these fluids exhibit either re-entrant melting or formation of cluster crystals at high densities. The latter phases are thermodynamically stable crystal phases that feature a lattice constant that is independent of density and, in turn, the occupancy of a lattice site increases linearly with In the present context, a coarse-... 

It has been shown by computer simulation [109-111] and density functional theory [106, 108] that the soft, purely repulsive, radially symmetric potential, V(r), will form cluster crystals at sufficiently high density if its Fourier transform, V(fe), becomes negative for a range of wave vectors. Within mean field approximation, the stability limit of the homogeneous liquid is given by the X-line [108]... 

The Gaussian form of the interaction potential, V, in Eq. (5.58) and the DPD-potential in Eq. (5.59) are particularly suitable because their Eourier transforms are nonnegative. Thus, Eq. (5.60) cannot be fulfilled and the liquid structure is stable against the formation of cluster crystals. 

Mladek et al., 2007] B. M. Mladek, P. Charbonneau, and D. FVenkel. Phase coexistence of cluster crystals Beyond the Gibbs phase rule. Physical Review Letters 99 235702, 2007. [Needham, 2002] P. Needham. The discovery that water is H2O. International Studies in the... 

---