Theoretical prediction of atomic and electronic structure of neutral Si[sub 6]O[sub m] (m=1–11) clusters (original) (raw)
Related papers
The Journal of Chemical Physics, 2004
The relationship between the polarizability, stability, and the geometry of small-size silicon clusters has been investigated by the density functional theory methods. Results obtained at local density approximation/Vosko-Wilk-Nusair and general gradient approximation/BLYP levels with polarized even-tempered basis set of quadruple quality are presented and compared with those obtained by the B3LYP method, as well as with the ab initio results in recent literature. We have found that the polarizability is directly related to the size of the energy gap between symmetry-compatible bonding and antibonding molecular orbitals, but not necessarily to the size of the HOMO-LUMO ͑highest occupied molecular orbital-lowest unoccupied molecular orbital͒ gap. Furthermore, we have defined two structural parameters, namely, the averaged Si-Si distances and the standard deviation of the Si-Si distances, which were found to correlate remarkably well with the binding energy of the clusters and the HOMO-LUMO gap, respectively. These straightforward correlations would, therefore, provide a means to predict the physical properties, in particular, the polarizability and the stability, simply based on the structural information of the cluster.
Modified genetic algorithms to model cluster structures in medium-sized silicon clusters: Siââ-Siââ
Phys Rev a, 2006
This paper presents the results obtained using a genetic algorithm ͑GA͒ to search for stable structures of medium-size silicon clusters. This is the third report in which a GA coupled with the MSINDO semiempirical molecular orbital program is used to find stable atomic cluster structures. The structures selected by the GA-MSINDO method were further optimized using the density functional theory ͑DFT͒. This combination of GA-MSINDO global optimization followed by DFT local optimization proves to be very effective for searching the structures of medium-size Si clusters. For most of the clusters studied here we report different structures with significant lower energy than those previously found using limited search approaches on common structural motifs. This demonstrates the need for global optimization schemes when searching for stable structures of medium-size silicon clusters.
Physical Review A, 2006
This paper presents the results obtained using a genetic algorithm (GA) to search for stable structures of medium size silicon clusters. In this work the GA uses a semiempirical energy function to find the best cluster structures, which are further optimized using density-functional theory. For small clusters our results agree well with previously reported structures, but for larger ones different structures appear. This is the case of Si 36 where we report a different structure, with significant lower energy than those previously found using limited search approaches on common structural motifs. This demonstrates the need for global optimization schemes when searching for stable structures of medium-size silicon clusters.
2006
Sin clusters in the size range n=4-35 have been investigated, using a combination of global structure optimization methods with DFT and ab-initio calculations. One of the central aims is to provide explanations for the structural transition from prolate to spherical outer shapes at about n=25, as observed in ion mobility measurements. First, several empirical potentials for silicon and a newly generated variant of one of them were better adapted to small silicon clusters, by global optimization of their parameters. The best resulting empirical potentials were then employed in global cluster structure optimizations. The most promising structures from this stage were relaxed further at the DFT level with a hybrid B3LYP functional. For the resulting structures, single point energies have been calculated at the LMP2 level with cc-pVTZ basis set. Results obtained at the DFT level strongly support the shape transition form prolate to spherical structures beginning with Si26. In contrast, ...
The Journal of chemical physics, 2013
The structures, energies, isomerization, and decomposition pathways of small ionic silicon oxide clusters, SiO(n)(+) (n = 3, 4), on doublet and quartet energy surfaces are investigated by density functional theory. New structural isomers of these ionic clusters have been obtained with this systematic study. The energy ordering of the isomeric cluster ions on doublet spin surface is found to follow the same general trend as that of the neutral ones, while it differs on the quartet surface. Our computational results reveal the energetically most preferred decomposition pathways of the ionic clusters on both spin surfaces. To comprehend the reaction mechanism, bonding evolution theory has also been employed using atoms in molecules formalism. The possible reasons behind the structural deformation of some isomers on quartet surface have also been addressed. Our results are expected to provide important insight into the decomposition mechanism and relative stability of the SiO(n)(+) clus...
Geometry and electronic structure of (SiO2)3 clusters
Russian Journal of General Chemistry, 2017
Electronic structure of (SiO 2) 3 clusters was calculated by the density functional method. Charge states were determined using various functionals, bond lengths and total energies of clusters were estimated.
Journal of Computational Chemistry, 2005
The magic number silica clusters [(SiO 2 ) n O 2 H 3 ] Ϫ with n ϭ 4 and 8 have been observed in the XeCl excimer laser (308 nm) ablation of various porous siliceous materials. The structural origin of the magic number clusters has been studied by the density functional theoretical calculation at the B3LYP/6-31G** level, with a genetic algorithm as a supplementary tool for global structure searching. The DFT results of the first magic number cluster are parallel to the corresponding Hartree-Fock results previously reported with only small differences in the structural parameters. Theoretical calculation predicts that the first magic number cluster (SiO 2 ) 4 O 2 H 4 and its anion [(SiO 2 ) 4 O 2 H 3 ] Ϫ will most probably take pseudotetrahedral cage-like structures. To study the structural properties of the second magic number cluster, geometries of the bare cluster (SiO 2 ) 8 , the neutral complex cluster (SiO 2 ) 8 O 2 H 4 , and the anionic cluster [(SiO 2 ) 8 O 2 H 3 ] Ϫ are fully optimized at the B3LYP/6-31G** level, and the corresponding vibrational frequencies are calculated. The DFT calculations predict that the ground state of the bare silica octamer (SiO 2 ) 8 has a linear chain structure, whereas the second magic number complex cluster (SiO 2 ) 8 O 2 H 4 and its anion [(SiO 2 ) 8 O 2 H 3 ] Ϫ are most probably a mixture of cubic cage-like structural isomers with an O atom inside the cage and several quasi-bicage isomers with high intercage interactions. The stabilization of these structures can also be attributed to the active participation of the group of atoms 2O and 4H (3H for the anion) in chemical bonding during cluster formation. Our theoretical calculation gives preliminary structural interpretation of the presence of the first and second magic number clusters and the absence of higher magic numbers.
2004
The relationship between the polarizability, stability, and the geometry of small-size silicon clusters has been investigated by the density functional theory methods. Results obtained at local density approximation/Vosko-Wilk-Nusair and general gradient approximation/BLYP levels with polarized even-tempered basis set of quadruple quality are presented and compared with those obtained by the B3LYP method, as well as with the ab initio results in recent literature. We have found that the polarizability is directly related to the size of the energy gap between symmetry-compatible bonding and antibonding molecular orbitals, but not necessarily to the size of the HOMO-LUMO ͑highest occupied molecular orbital-lowest unoccupied molecular orbital͒ gap. Furthermore, we have defined two structural parameters, namely, the averaged Si-Si distances and the standard deviation of the Si-Si distances, which were found to correlate remarkably well with the binding energy of the clusters and the HOMO-LUMO gap, respectively. These straightforward correlations would, therefore, provide a means to predict the physical properties, in particular, the polarizability and the stability, simply based on the structural information of the cluster.
Theoretical study of the structural evolution of small hydrogenated silicon clusters: Si6Hx
Chemical Physics Letters, 1996
Density functional calculations were performed for the structural properties and energetics of small hydrogenated silicon clusters: Si6Hx (0 ~< x ~< 14). We find that the structures of Si6Hx can be classified into several distinct families in terms of the arrangement of silicon atoms. In particular, we find a series of structures which are intermediate between compact and tetrahedral atomic arrangements. Based on calculated formation energies we address the relative stability of the Si6Hx clusters.
Structures and energetics of Si6Hx and Si6H+x clusters
Surface Science, 1997
We have investigated the hydrogenation-induced structure evolution of small silicon clusters (Si, and Si,i). We found that structures of S&H, and S&H: can be classified into several distinct families in terms of the arrangement of Si atoms, and that ionization affects the relative stability of these structure families. We also found that for the sequence Si,H,_, + H, +Si,H, or S&H:_, + Hz *S&Hz, hydrogenation proceeds in substantially different manners in low-and high-x regimes.