Reactions of silicon cluster ions, Si+n (n=10–65), with water

Abstract

The chemical reactions of size selected Si+n (n=10–65) with D2O have been studied using injected ion drift tube techniques between temperatures of 258 and 404 K. The only products detected were a series of Sin(D2O)+m adducts. Large variations in reactivity were observed for the smaller clusters (n<40) that diminish with increasing cluster size. Si+11, Si+13, Si+14, Si+19, and Si+23 are particularly unreactive compared to their neighbors. At room temperature the larger clusters (n>40) are a factor of ∼10–1000 (depending on the bulk surface) less reactive towards water than bulk silicon. The reaction rates for all clusters exhibit an unusually strong negative temperature dependence but are independent of the buffer gas pressure. These results suggest that the reaction mechanism probably involves two steps. In the first step, a weakly bound molecularly adsorbed Si+n⋅⋅⋅D2O adduct is produced. The second step involves rearrangement to give a more strongly bound (and probably dissociatively adsorbed) SinD2O+ product. It appears that the reaction rates for some of the smaller clusters show a faster than linear dependence on D2O pressure. One possible explanation for this unusual observation is that a second D2O molecule solvates the transition state and significantly lowers the activation barrier for dissociative adsorption.

High‐spin silicon fullerene Si60 and its oligomers

“…3 As seen from Table II, the behavior of the composite is similar to that of the Si 60 C 60 . As in the latter case, the structure of the Si 60 H 60 in both spin configurations is practically the same, while the energy of the singlet state is considerably lower so that the species should be stable in the ground state and nonmagnetic.…”

“…The structures of the spin-triplet and -singlet chains cannot be distinguished by eye. The oligomer heats of oligomer formations alongside with the energies of molecule bonding in the oligomers related to one monomer molecule, E bn , are 3 Effect is similar to the hydrogenation of open surfaces of silicon crystal [15]. summarized in Table III.…”

“…Nevertheless, despite the fact that numerous attempts to synthesize or find out silicon fullerenes have been undertaken practically at once after the discovery of its carbon analogs, there is a lack of direct evidence of the species' existence. As occurred, silicon clusters with open bare surface can be received in molecular beams only under high vacuum (see [2,3] and reference therein). Low density of the clusters makes it impossible to carry out some reliable determination of their composition and structure.…”

Computational studies of small (AlP)N clusters

“…For this reason, the past few years have witnessed enormous scientific activity in the experimental and theoretical investigations of semiconductor clusters of nanometer dimensions [2][3][4]. In this paper we examine evolution of (AlP) N cluster structures using density functional calculations and compare the results with the corresponding geometries of Si 2N clusters.…”

“…36.40+d; 61.43.Bn; 61.46.+w; 68.35.Bs; 82.65.My As the drive towards miniaturization of electronic devices accelerates, there is a pressing need to investigate the properties of low-dimensional semiconductors [1]. For this reason, the past few years have witnessed enormous scientific activity in the experimental and theoretical investigations of semiconductor clusters of nanometer dimensions [2][3][4]. In this paper we examine evolution of (AlP) N cluster structures using density functional calculations and compare the results with the corresponding geometries of Si 2N clusters.…”