Silicon cluster

Patterson C H and Messmer R P 1990 Bonding and structure in silicon clusters a valence-bond interpretation Phys. Rev. B 42 7530... 

Silicon cluster reactions are an example of a newly emerging field of research which is very amenable to study with electronic structure methods. This exercise will examine the potential surface for silicon cation reacting with silane (SiH4). Such reactions are central to the growth of large silicon clusters, which occurs by sequential additions of -SiHj ... 

Silicon Cluster Reactions S t 2 Reaction Hydration Reactions... 

F. S. Khan and J. Q. Broughton, Simulation of Silicon Clusters and Surfaces via Tight-Binbding Molecular Simulations, Phys. Rev. B 39 3688 (1989)... 

The ultrahigh vacuum STM was used to investigate the addition of the 2,2,6,6-tetramethyI-l-piperidinyloxy (TEMPO) radical to the dangling bond of Si(l 0 0)-2 X 1 surface. ° ° The TEMPO can bond with a single dangling bond to form stable Si-O coupling products, in contrast to the thermal decomposition of TEMPO-silicon compounds. Semiempiiical and DFT calculations of TEMPO bound to a three-dimer silicon cluster model yielded... 

The redox chemistry of stannyl metalcarbonyl clusters has been studied in one case177. CV of the cluster PhSnCo3(CO)i2 shows an irreversible reduction peak —0.74 V vs Ag wire, at 100 mV s 1. Faster scans were not reported. It is concluded that the radical anion [PhSnCo3(CO)i2r is unstable, in contrast to the silicon cluster PhSiCo3(CO)n which gives a stable radical anion (reported lifetime of 2.3 s) at —0.26 V (200 mV s 1). 

A few clusters of interest containing germanium and transition metals have been reported.136-138 Dimethylgermane was found to replace only the bridging carbonyls between cobalt in a mixed germanium/cobalt/iron cluster complex (Equation (107)), and replacement of the carbonyl bridging the iron metal centers was not observed.137 A similar reaction leads to replacement of a bridging carbonyl in a mixed cobalt/silicon cluster (Equation (108)).136... 

Rev. A., 73, 053203 (2006). Modified Genetic Algorithm to Model Cluster Structures in Medium-Sized Silicon Clusters Si18-Sifi0-... 

Investigation of Prolate andNear Spherical Geometries of Mid-Sized Silicon Clusters. 

Clusters of the elements aluminum to thallium containing only one or two carbon atoms and strong direct element-element interactions, similar to boron rich car-baboranes, have not yet been synthesized, and also the corresponding silicon derivatives are relatively rare. To the best of our knowledge only one aluminum-silicon and one gallium-silicon cluster (1 and 2) has been reported in the literature. The reaction of metastable aluminum(I) chloride with decamethylsilicocene or with a mixture of SiCl4 and (AlCp )4, respectively, afforded black crystals of... 

Fig. 7.15 I ncrease in bandgap energy AEc with decreasing diameter of a silicon cluster or dot (open symbols) or a silicon wire (filled symbols), as predicted by various theoretical investigations.

Theoretical investigations of AEV and AEC have indicated that the ratio AEV/AEC is greater than 1 [Zh2, Vo2, Ne2] and may be as high as 3 for the case of hydrogenated silicon clusters [Re3], In a similar calculation for thin silicon films, even-odd oscillations of A v according to the number of Si monolayers have been found [Zh2], For the latter case the ratio AEy/AEc showed values between 1 and 2. The results of a study [Wa5] including the decrease in the static dielectric constant with size are close to the experimentally [Bu2] observed values of about 2 for the ratio AEy/AEc, as shown in Fig. 7.16. In this work [Wa5], it is concluded that the electron-hole pair is confined by the physical dimension of the quantum dot, not by Coulomb attraction. 

Fig. 7.16 CB edge shifts versus VB edge shifts calculated for silicon clusters under different assumptions for the value of the dielectric constant s (lines). After [Wa5]. For comparison the experimental results obtained by...

A visible red luminescence corresponds to a silicon cluster size between about 1 and 2.5 nm. 

With roughly 1000 atoms, the size of the silicon clusters that constitute the micro PS network is between the bulk crystal and a molecule. Hence models of the luminescence process based on size reduction of the crystal, as well as models based on molecular sttuctures, have been proposed, which are reviewed in detail in [Ca7, Ju3]. Generally the various models of the luminescence of PS can be classified into three major categories ... 

The visible luminescence from PS has been ascribed to QC effects [Cal]. This interpretation is supported by the observation of a similar luminescence from silicon clusters in the nanometer regime or large silicon molecules that are not produced by anodization but by alternative methods. 

The results of this study are somewhat atypical in the sense that the inferred re and tq structures of Sis are nearly the same. This is a somewhat fortuitous circumstance, which cannot be attributed entirely to the fact that Sis appears to be only weakly anharmonic (see cubic constants in Table I), since it has a relatively low-frequency bending mode that is potentially problematic. Nonetheless, it can be stated with some certainty that the structure obtained in the present research is accurate to within 0.002A and 0.2 . Hence, this structure can be used as a reference for benchmarking quantum chemical methods intended for high accuracy calculations on silicon clusters, as well as for comparison with structures of other silicon-containing molecules. 

The silicon cluster contained 60 samples and a normalized concentration of 92% silicon. This cluster was estimated to be entirely quartz. Only the quartz test vector provided an adequate fit upon rotation of one or two eigenvectors. 

King RB, Heine T, Corminboeuf C et al (2004) Antiaromaticity in bare deltahedral silicon clusters satisfying Wade s and Hirsch s mles an apparent correlation of antiaromaticity with high symmetry. J Am Chem Soc 126 430 31... 

The silicon clusters are formed in the inlet region at relatively low temperatures. As the temperature increases the formed Si clusters will thermally decompose and be available for growth. This is very similar to HTCVD however, in this case there is no sublimation, only a decomposition of the Si clusters. 

Figure 5.18. Calculated reaction path and optimized structures using DFT for (a) N—H dissociation and (b) N—CH3 dissociation of dimethylamine on the one-dimer silicon cluster. Figure reused with permission from Collin Mui, Journal of Chemical Physics, 114, 10170 (2001). Copyright 2001, American Institute of Physics [279].

The structure of ionic silicon clusters, the mixed silicon-carbon species and their reactions with neutral molecules have been investigated by a number of experimental151,120-133 and theoretical groups134-137. Ion-molecule reactions of the silicon clusters have also been thoroughly studied by larrold and coworkers51. These... 

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