Analogy of silicon clusters with deltahedral boranes: How far can it go? Reexamining the structure of Sin and Sin2−, n=5–13 clusters

Nonlinear effects in infrared action spectroscopy of silicon and vanadium oxide clusters: experiment and kinetic modeling

Nonlinear effects in infrared action spectroscopy are experimentally quantified and successfully modeled for different inorganic clusters.

Density functional studies of small silicon clusters adsorbed on graphene

The structural and electronic properties of small Si_n clusters (n = 1–6, 10) adsorbed on graphene are studied by use of density functional theory within periodic boundary conditions.

Theoretical study of the Si(5-n)(BH)n2- and Na(Si(5-n)(BH)n)- (n = 0-5) systems

The potential energy surfaces of the Na(Si(5-n)(BH)(n))(-) and Si(5-n)(BH)(n)(2-) (n = 0-5) systems have been explored in detail. We established that all the global minimum structures of anionic and dianionic systems can be obtained by substitution of one or more silicon atoms of the global minima of NaSi(5)(-) and Si(5)(2-) for B-H units. The conservation of the overall structure upon isoelectronic substitution was shown to be due to the preservation of the chemical bonding pattern. Theoretical VDEs were calculated for all of the sodiated Na(Si(5-n)(BH)(n))(-) (n = 0-5) systems to facilitate their experimental detection.

An ab initio calculation study of silicon and carbon binary clusters C7Si(n) (n = 1-7)

Binary C(7)Si(n) (n = 1-7) clusters are studied using density functional calculations at the level of B3LYP/6-311G(d). Lowest-energy structures have been determined theoretically and their properties such as binding energies, second differences in energy and highest-occupied and lowest-unoccupied molecular orbital gaps have been analyzed. It is found that the lowest-energy structures of the C(7)Si(n) (n = 1-7) clusters change from linear to planar when n ≥ 3, and in the planar structures C atoms prefer to form five- and six-membered rings surrounded by extra Si atoms in the form of the C(2)Si units.

Designing novel Sn-Bi, Si-C and Ge-C nanostructures, using simple theoretical chemical similarities

A framework of simple, transparent and powerful concepts is presented which is based on isoelectronic (or isovalent) principles, analogies, regularities and similarities. These analogies could be considered as conceptual extensions of the periodical table of the elements, assuming that two atoms or molecules having the same number of valence electrons would be expected to have similar or homologous properties. In addition, such similar moieties should be able, in principle, to replace each other in more complex structures and nanocomposites. This is only partly true and only occurs under certain conditions which are investigated and reviewed here. When successful, these concepts are very powerful and transparent, leading to a large variety of nanomaterials based on Si and other group 14 elements, similar to well known and well studied analogous materials based on boron and carbon. Such nanomaterias designed in silico include, among many others, Si-C, Sn-Bi, Si-C and Ge-C clusters, rings, nanowheels, nanorodes, nanocages and multidecker sandwiches, as well as silicon planar rings and fullerenes similar to the analogous sp2 bonding carbon structures. It is shown that this pedagogically simple and transparent framework can lead to an endless variety of novel and functional nanomaterials with important potential applications in nanotechnology, nanomedicine and nanobiology. Some of the so called predicted structures have been already synthesized, not necessarily with the same rational and motivation. Finally, it is anticipated that such powerful and transparent rules and analogies, in addition to their predictive power, could also lead to far-reaching interpretations and a deeper understanding of already known results and information.

A Stochastic Search for the Structures of Small Germanium Clusters and Their Anions: Enhanced Stability by Spherical Aromaticity of the Ge10 and Ge12(2-) Systems

Investigations on germanium clusters in the neutral, anionic, and dianion states Gen(x) (n = 2-12 and x = 0, -1, -2) are performed using quantum chemical calculations with the B3LYP functional and the coupled-cluster singles and doubles [CCSD(T)] methods, in conjunction with the 6-311+G(d) basis set. An improved stochastic method is implemented for searching the low-lying isomers of clusters. Comparison of our results with previous reports on germanium clusters shows the efficiency of the search method. The Ge8 system is presented in detail. The anionic clusters Gen(-/2-) are studied theoretically and systematically for the first time, and their energetics are in good agreement with available experiments. The clusters Ge10, Ge10(2-), and Ge12(2-) are, in their ground state, characterized by large highest occupied molecular orbital-lowest unoccupied molecular orbital gaps, high vertical and adiabatic detachment energies, and substantial average binding energies. The enhanced stability of these magic clusters can consistently be rationalized using the jellium electron shell model and the spherical aromatic character.

Heteroborane analogs of silicon clusters: experimental and theoretical studies on Bi2Si5 and Bi2Si5(-)

We have investigated the electronic structure of anionic and neutral Bi(2)Si(5) by means of anion photoelectron spectroscopy and density functional calculations. Both the experiments and calculations reveal that the Bi(2)Si(5)(-) anion prefers to adopt a distorted trigonal-bipyramidal structure with Bi(2) bridges. Following the isolobal analogy between divalent Si and B-H group, we show that both neutral Bi(2)Si(5) and neutral Bi(2)B(5)H(5) adopt similar pentagonal-bipyrmidal geometries and have analogous orbital energy patterns.

A new class of silicon-carbon clusters: a full study of the hydrogenated SinC2H2, n=3,4,5, clusters in comparison with their isoelectronic carboranes C2BnHn+2

The structural and electronic characteristics of the Si(n)C(2)H(2), n=3,4,5, clusters are studied by ab initio calculations based on coupled cluster and density functional theory using the hybrid B3LYP functional. It is demonstrated that all three clusters are structurally and electronically homologous to the corresponding isoelectronic organometallic carboranes C(2)B(n)H(n+2). This homology, which is in full agreement with the analogy of Si(6) (2-) and B(6)H(6) (2-) demonstrated recently by the author [J. Chem. Phys. 127, 014314 (2007)], includes not only the ground states but also the lower-lying isomers as well. These lowest lying isomers can be obtained by ortho, para, and meta substitutions from the corresponding Si(n) (2-), n=3,4,5, dianions. The energetic ordering of the low-lying isomers is in full agreement with the known valence and topological charge stability rules developed for carboranes. The hydrogenated clusters are much more stable than their nonhydrogenated counterparts. It is suggested that Si(3)C(2)H(2), Si(4)C(2)H(2), and Si(5)C(2)H(2), which can be probably found in interstellar space, are special examples of a general class of silicon-carbon clusters of the form Si(n)C(2)H(2), with analogous properties and similarities to the corresponding carboranes C(2)B(n)H(n+2). It is furthermore illustrated that the lowest energy structures of the Si(n)C(2) clusters can be obtained through a systematic and straightforward procedure from the Si(n)C(2)H(2) clusters. The present results could hopefully make possible the exploitation of the rich borane and carborane chemistry for the design and development of novel silicon and silicon-carbon composite nanomaterials.