Polygonal model for layered inorganic nanotubes

Multiwalled inorganic nanotubes with circular cross sections must have either an incoherent interface or a large amount of strain. However, nanotubes with a polygonal cross section can have a coherent interface with considerably less strain. We present a model for polygonal nanotubes with no defects where the chirality of the nanotube determines the shape of the cross section. Circular and polygonal nanotubes are compared based on their strain energy and interfacial energy. We have used first-principles calcuations to parameterize strain and interfacial energy for TiS2 nanotubes. These calculations show that the polygonal model is energetically favorable to the circular model when the inner radius is above a critical radius, 6.2 Å for a TiS2 nanotube with ten layers. These results should provide insight into further investigations of nanotube structure and allow computational studies to more accurately predict nanotube properties.