Polygonal model for layered inorganic nanotubes

Abstract

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 TiS 2 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 TiS 2 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.

TiS2and ZrS2single- and double-wall nanotubes: First-principles study

“…Although we were not able to obtain the completely polygonal DWNTs proposed by Tibbetts et al, we can assume that the advantage of the multiwall NTs with a polygonal‐cross section over the NTs with a circular cross‐section will rise with increasing of the NT diameter and it becomes more probable in the outer shells of the multiwall NTs.…”

Structure and stability of SnS2-based single- and multi-wall nanotubes

“…tain the completely polyhedral DWNTs proposed by Tibbetts et al[67],564 we can conclude that the advantage of the multi-wall nanotubes with a565 polygonal cross-section of external shells over the nanotubes with a cir-566 cular cross-section of all shells will rise with increasing number of walls 567 in the MWNT. Unfortunately, it is difficult to recognize on HRTEM im-568 ages of synthesized multi-layered disulfide NTs a small deviation from 569 purely circular cross-section.…”

“…For this purpose, we have calculated 530 several DWNTs starting from both the cylindrical and polyhedral shapes.531As example, inFig. 8awe show the initial hexahedron structure of 532 (12, 12)@(18, 18)@(24, 24) NT for which the coherence[67] of the 533 flat segments is virtually satisfied. Nevertheless, the geometry optimiza-534 tion has led to the same, almost cylindrical shape(Fig.…”

First‐principles Calculations of InS‐based Nanotubes

“…Generally, the polyhedral shape of the SWNT results in a higher strain energy, because the bending radius is smaller at the corners. However, as supposed by Tibbetts et al., this can be compensated by the reduced interfacial energy of the flat sectors. This energy reduction occurs because the flat sections of the nanotube can have a coherent interface with no tensile strain.…”