Dimerization Effects and Negative Strain Energy in Silicon Monosulfide Nanotubes

We report on the construction and characterization of silicon monosulfide nanotubes that were obtained by rolling up two-dimensional materials isoelectronic to phosphorene in the recently discovered layered Pmma and β phases. We relaxed and studied the nanotube structures using computational methods within density functional theory (DFT). We found that the nanotubes with a thick Pmma layer remain stable at room temperature, and their electronic properties depend on their diameters. Small-diameter nanotubes display metallic character, while nanotubes with increasing diameter show semiconducting ground states due to the dimerization in the silicon-silicon distances that opens a gap, leading to interesting optical properties in the near-infrared region. Furthermore, we discovered β SiS monolayer nanotubes having negative strain energies, similar to the well-known imogolite inorganic nanotubes. The combined thermal stability, compelling optical properties, and diverse applications of these silicon monosulfide nanotubes underscore the demand for novel synthesis methods to fully explore their potential in various fields.