Synthesis and Temperature-Dependence of Hydrogen-Terminated Silicon Clusters

Rechtsteiner, Gregory A.; Hampe, and Oliver; Jarrold, Martin F.

doi:10.1021/jp004223n

Cited by 44 publications

(24 citation statements)

References 83 publications

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“…2͒ and therefore in the family of Si n H n cages, the n = 14 cage is not magic and we do not expect it to be highly abundant. Note that in experiments 17 there is a somewhat broad distribution of Si 14 H x clusters as a function of x and the maximum occurs at x = 14. On the other hand, cages with n = 16 and 20 are particularly stable and magic.…”

Section: A Empty Cagesmentioning

confidence: 90%

“…In such studies hydrogen is used to passivate a bare silicon nanoparticle, which is generally assumed to have the bulk diamond structure. Recent experiments 17 suggest that Si n H n clusters can be produced in the laboratory by proper control of temperature and relative fractions of Si and H atoms. Here we present a detailed study of Si n H n cages with n = 8, 10,12,14,16,18,20,24, and 28 and also show that similar structures are stable for Ge and Sn.…”

Section: Introductionmentioning

confidence: 99%

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Hydrogenated caged clusters of Si, Ge, and Sn and their endohedral doping with atoms:Ab initiocalculations

Kumar

Kawazoe

2007

Phys. Rev. B

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We report results of an ab initio study on the stability of hydrogenated empty cages X n H n with X = Si, Ge, and Sn, and n = 8,10,12,14,16,18,20,24,and 28. All these cages have large highest-occupied-lowestunoccupied molecular orbital ͑HOMO-LUMO͒ gaps. The HOMO-LUMO gap for Ge cages is found to be even larger than the values for Si cages, though in bulk Ge has a smaller band gap than Si. Cages with n = 16 and 20 are found to be particularly stable in the form of fullerene structures. The bonding in the dodecahedral X 20 H 20 cage is very close to sp 3 type and it leads to the highest stability of this cage with perfect icosahedral symmetry. Endohedral doping of the empty cages such as Si n H n ͑n =10-28͒, with different guest atoms shows that doping can be used to manipulate the HOMO-LUMO gap with the possibility of varying their optical properties as well as to prepare species with large magnetic moments. Depending upon the guest atom, the character of the HOMO and the LUMO states and their origins either from the cage or the guest atom changes. This could lead to their applications in sensors. In contrast to the metal-encapsulated silicon-caged clusters, the embedding energy of the guest atom in the hydrogenated silicon fullerenes is small in most cases due to the weak interactions with the cage and therefore these slaved guest atoms can keep their atomic properties to a large extent. We find that atoms with closed electronic shell configurations such as Ca, Ba,… generally occupy the center of the cage. However, Be and other open electronic shell atoms tend to drift towards the wall of the cage. Doping of halogens such as iodine and alkalis such as Na can be used to produce, respectively hole and electron doping while transition-metal atoms such as V, Cr, Mn, and Fe are shown to produce atomiclike magnetic moments in many cases. In most of these cases the HOMO-LUMO gap becomes small because the guest atom orbital͑s͒ are only partially occupied. However, for Ni and Zn the HOMO-LUMO gap is large as the hybridized d orbitals become fully occupied. An interesting finding is that the endohedral doping can lead to a higher-energy undoped cage isomer to become the lowest-energy doped isomer. Implications of this result for endohedral fullerenes of carbon are also discussed.

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Section: A Empty Cagesmentioning

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Hydrogenated caged clusters of Si, Ge, and Sn and their endohedral doping with atoms:Ab initiocalculations

Kumar

Kawazoe

2007

Phys. Rev. B

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“…Nanoparticles and nanocrystals of Si can be prepared by plasma enhanced chemical vapor deposition. [5][6][7] Laser ablation of Si wafer 8 and thermal vaporization of melted Si ͑Ref. 9͒ may also be used to prepare Si nanoclusters.…”

Section: Introductionmentioning

confidence: 99%

Internal pressure and surface tension of bare and hydrogen coated silicon nanoparticles

Hawa

Zachariah

2004

The Journal of Chemical Physics

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Public Reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. We present a study of internal pressure and surface tension of bare and hydrogen coated silicon nanoparticles of 2-10 nm diameter as a function of temperature, using molecular dynamics simulations employing a reparametrized Kohen-Tully-Stillinger interatomic potential. The internal pressure was found to increase with decreasing particle size but the density was found to be independent of the particle size. We showed that for covalent bond structures, changes in surface curvature and the associated surface forces were not sufficient to significantly change bond lengths and angles. Thus, the surface tension was also found to be independent of the particle size. Surface tension was found to decrease with increasing particle temperature while the internal pressure did not vary with temperature. The presence of hydrogen on the surface of a particle significantly reduces surface tension ͑e.g., drops from 0.83 J/m 2 to 0.42 J/m 2 at 1500 K͒. The computed pressure of bare and coated particles was found to follow the classical Laplace-Young equation.

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“…2 Furthermore, (SiH) n cages up to n ) 22 have been produced by laser photolysis. 33 While the nanostructures may require novel synthetic approaches, the existing experimental techniques could offer useful guidelines.…”

Section: Resultsmentioning

confidence: 99%

Icosahedral Polygermane and Polystannane Nanostructures

2007

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Stable I h -symmetric polygermane and polystannane nanostructures have been predicted on the basis of quantum chemical calculations. Structures, stabilities, and electronic properties of cages up to Ge 500 H 500 and Sn 500 H 500 were determined. The facets of the icosahedral cages resemble the monolayer sheets of experimentally known layered GeH. The stabilities and electronic properties of the cages converge toward the corresponding monolayer sheets. Due to their electronic properties, the polygermane and polystannane nanostructures may turn out to be useful in optical applications.

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Synthesis and Temperature-Dependence of Hydrogen-Terminated Silicon Clusters

Cited by 44 publications

References 83 publications

Hydrogenated caged clusters of Si, Ge, and Sn and their endohedral doping with atoms:Ab initiocalculations

Hydrogenated caged clusters of Si, Ge, and Sn and their endohedral doping with atoms:Ab initiocalculations

Internal pressure and surface tension of bare and hydrogen coated silicon nanoparticles

Icosahedral Polygermane and Polystannane Nanostructures

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