Bonding and stabilities of small silicon clusters: A theoretical study of Si7–Si1

Raghavachari, Krishnan; Rohlfing, Celeste McMichael

doi:10.1063/1.455065

Cited by 465 publications

(210 citation statements)

References 56 publications

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“…In this case cages are predicted for upwards of 4 atom clusters. The 6 and 7 atom structures predicted are in agreement with recent experimental results [25,26]. An interesting atom structures are predicted to have a lower energy with this parameterisation.…”

Section: ¡ ©supporting

confidence: 80%

The structure of atomic and molecular clusters, optimised using classical potentials

Ali

Smith

Hobday

2006

Computer Physics Communications

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The problem of the determination of the minimum energy configuration of an arrangement of point particles under the interaction of their interatomic forces is discussed. The interatomic forces are described by classical many body potentials. Different optimisation methods are considered, multi level single link, topographical differential evolution and a genetic algorithm but it is shown that genetic algorithms combined with an efficient local optimisation method is especially quick and reliable for this task. In addition to comparing some different optimisation methods, the structures of clusters of atoms described by interatomic potential functions containing up to a few hundred atoms are calculated including some with some special symmetries. A number of applications are given including covalent carbon and silicon clusters, close-packed structures such as argon and silver and the two-component carbon-hydrogen system.

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Section: ¡ ©supporting

confidence: 80%

The structure of atomic and molecular clusters, optimised using classical potentials

Ali

Smith

Hobday

2006

Computer Physics Communications

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“…This is because the bonding feature of the Si 5n H 10 (n is an integer) clusters is very similar to that of the infinite SWSNTs; namely, the coordination number of every Si atom (except those at the ends) is fourfold. Note that previous ab initio calculations have shown that small-sized silicon clusters tend to favor a higher coordination number than fourfold (22)(23)(24). Hence, without the hydrogen termination at the ends, the stacked-pentagon silicon clusters will be unstable.…”

mentioning

confidence: 98%

Metallic single-walled silicon nanotubes

Bai

Zeng²,

Tanaka³

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

130

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Atomistic computer-simulation evidences are presented for the possible existence of one-dimensional silicon nanostructures: the square, pentagonal, and hexagonal single-walled silicon nanotubes (SWSNTs). The local geometric structure of the SWSNTs differs from the local tetrahedral structure of cubic diamond silicon, although the coordination number of atoms of the SWSNTs is still fourfold. Ab initio calculations show that the SWSNTs are locally stable in vacuum and have zero band gap, suggesting that the SWSNTs are possibly metals rather than wide-gap semiconductors.L ow-dimensional nanostructures are known to have properties that can be markedly different from their bulk counterparts. For example, as shown in a recent experiment (1), Ho and coworkers demonstrated atom-by-atom evolution of electronic band structure of 1D gold chain. For semiconductor nanostructures, when the carriers (electrons and holes) are confined to dimensions less than their de Bröglie wavelength (typically a few nanometers), quantum-mechanical size effects can emerge. The carrier confinement at the nanoscale can be in 0D (quantum dots), 1D (quantum wires), or 2D (quantum wells) (2). Indeed, the current interest in fabricating low-dimensional semiconductor nanostructures, coined as band-structure engineering, has largely relied on novel quantum-mechanical size effects.The crystalline structure of 3D bulk silicon is cubic diamond, similar to that of carbon diamond. However, unlike the carbon counterpart (3), a 1D single-walled silicon nanotube (SWSNT) has not been found in nature yet, largely because silicon prefers sp 3 bonds rather than sp 2 bonds (4). Indeed, silicon has been viewed as nontubular solid rather than tubular solid, similar to carbon and boron nitride. The cubic diamond silicon is known as a semiconductor with an energy band gap of 1.17 eV (1 eV ϭ 1.602 ϫ 10 Ϫ19 J). At high pressures, however, the cubic-diamondstructured silicon can undergo a phase transformation to highly coordinated (sixfold or above) metallic phases such as the ␤-tin and hexagonal closed-packed structures (5). To date, experimentally produced 1D-like nanostructures of silicon [e.g., porous silicon (6) and silicon nanowires (7-12)] all assume either the cubic diamond crystalline structure or the local structure of amorphous silicon. A commonly reported electronic property of the 1D silicon nanostructures is that they all have wider band gap than the cubic diamond silicon. Here we present atomistic computer-simulation evidences of three thinnest SWSNTs: the square, pentagonal, and hexagonal silicon nanotubes. The local geometric structure of these SWSNTs differs from that of cubic diamond silicon and the surface-passivated 1D silicon nanowires. It also differs from that of the carbon-nanotube-like ''hypothetical'' SWSNTs (4, 13-15), because the latter types of SWSNTs are composed of both sp 3 and sp 2 bonds. Moreover, ab initio quantum-mechanical calculations show that the present SWSNTs exhibit an entirely opposite trend in the band-gap change compared wi...

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“…The true equilibrium state under all of these conditions is nearly complete conversion of silane to crystalline silicon and molecular hydrogen. Equilibrium calculations that included pure silicon clusters Si n (1 e n e 10), using the same thermochemistry discussed in previous work, 34,52,57 predicted that the Si 7 cluster would be the dominant cluster present at partial equilibrium among the pure silicon clusters and the species shown in Figure 2. However, in the kinetic simulations presented below, formation of pure silicon clusters was found to be unimportant compared to formation of hydrogenated silicon clusters.…”

Section: Thermochemistry Of the Silicon Hydridesmentioning

confidence: 99%

Thermochemistry and Kinetics of Silicon Hydride Cluster Formation during Thermal Decomposition of Silane

1998

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Product contamination by particles nucleated within the processing environment often limits the deposition rate during chemical vapor deposition processes. A fundamental understanding of how these particles nucleate could allow higher growth rates while minimizing particle contamination. Here we present an extensive chemical kinetic mechanism for silicon hydride cluster formation during silane pyrolysis. This mechanism includes detailed chemical information about the relative stability and reactivity of different possible silicon hydride clusters. It provides a means of calculating a particle nucleation rate that can be used as the nucleation source term in aerosol dynamics models that predict particle formation, growth, and transport. A group additivity method was developed to estimate thermochemical properties of the silicon hydride clusters. Reactivity rules for the silicon hydride clusters were proposed based on the group additivity estimates for the reaction thermochemistry and the analogous reactions of smaller silicon hydrides. These rules were used to generate a reaction mechanism consisting of reversible reactions among silicon hydrides containing up to 10 silicon atoms and irreversible formation of silicon hydrides containing 11-20 silicon atoms. The resulting mechanism was used in kinetic simulations of clustering during silane pyrolysis in the absence of any surface reactions. Results of those simulations are presented, along with reaction path analyses in which key reaction paths and rate-limiting steps are identified and discussed.

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Bonding and stabilities of small silicon clusters: A theoretical study of Si7–Si1

Cited by 465 publications

References 56 publications

The structure of atomic and molecular clusters, optimised using classical potentials

The structure of atomic and molecular clusters, optimised using classical potentials

Metallic single-walled silicon nanotubes

Thermochemistry and Kinetics of Silicon Hydride Cluster Formation during Thermal Decomposition of Silane

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