Shedding light on the self-assembly of stable SiC based cage nanostructures: A comprehensive molecular dynamics study

A comprehensive molecular dynamics study to shed light on the existence of SiC based cage nanostruc-tures Si m C n , together with their stability, structural and other properties, in the range of compositions with n/(n + m) from 0.4 to 0.6 has been carried out using an efficient semi-empirical Hamiltonian scheme. Through this study, a series of self-assembled stable (even up to 2000 K) SiC based Si m C n cage structures are predicted. The mechanism of the stability and structural properties of the stable Si m C n caged structures are analyzed in terms of their composition, bonding nature, surface environment, local strain, and types of ring structures. It is found that, for a given composition, the existence of the Si–C bonds, the sp 2 bonding nature between the Si and C atoms, and the role played by the environmental mediation are crucial in forming the self-assembled and stable SiC cage structures. In particular, a ''mending'' process dictated by an environment-driven self-assembly is provided to show the possible transition from one stable cage structure to another cage structure of similar composition which might occur in the synthesis. The oscillatory behavior of the HOMO–LUMO gap as a function of the diameter of Si m C n cages is also observed as expected. This work provides a possible path way for fabricating SiC based nano-cage structures. The exceptional intrinsic properties of bulk SiC (e.g., low density, high strength, high thermal conductivity, high index of refraction, low thermal expansion, and wide band gap, etc.) have attracted tremendous interests for the development of SiC based nano-scale materials, not only because of their promising technological applications but also the diversity in their structures and bonding nature. Recently, the variety of SiC based nanostructures that include sp 2-like bonded graphitic sheets and single-walled SiC nanotubes [1] and the sp 3-bonded nanowires [2] have been studied. The SiC graphitic sheet and single-walled nanotubes have been found to exhibit semiconducting behaviors (e.g., the indirect band gap feature found in the SiC graphitic sheets and armchair single-walled nanotubes, and the direct band gap feature found in the zigzag SiC nanotubes). Induced by surface reconstructions, the SiC nanowires have been found to exhibit a gapless feature when the diameter of the wires is less than $4 nm, except the 2H–SiC nanowires which still exhibit semiconducting nature. In particular, a new SiC nanostructure, the bucky-diamond structures with a mixture …