Rolling up Two-Dimensional Layers of Silicon Sulfide: Dimerization Effects and Negative Strain Energy in Silicon Monosulfide Nanotubes*

We investigate nanotubes of two-dimensional materials isoelectronic to phosphorene by rolling up the recently discovered layers of silicon monosulfide, in phases that in order of decreasing stability are labeled as P_mma and β [1-3]. We find that the nanotubes of thick layer P_mma silicon monosulfide grown around 1 nm in diameter are stable at room temperature. The nanotubes having small diameters show metallic character, and with increasing diameter, they become semiconductors because gaps are open by the dimerization of the silicon-silicon distances. Lying at higher energy, we also find that the β SiS monolayer nanotubes are stable with negative strain energy, similar to imogolite nanotubes. The theoretical thermal stability of these two types of silicon monosulfide nanotubes showing such intriguing properties would request further to investigate procedures for their novel synthesis by experimentalists.
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