Helicity analysis of single, double, and triple helical iodine chains inside single-walled silicon carbide nanotubes

Abstract

The helicity of encapsulated single, double, and triple helical iodine chains inside single-walled silicon carbide nanotubes is studied using the van der Waals interaction potential and density functional theory (DFT). Our results show that the optimal radius of the helical iodine chain increases linearly with tube radius, which produces a constant separation between the encapsulated chain and tube wall. The optimal helical angle cannot be determined with a single helical chain, due to the absence of the inter-chain interaction. For the double and triple helical chains, a small optimal helical angle can be induced by a large inter-chain interaction for the same tubes or a large tube for the same chain structure. We also find that the helicity is insensitive to the tube chirality. The DFT calculation further justifies our classical force field analysis and provides a more comprehensive understanding of this helical chains configuration.