DFT modeling of electronic and mechanical properties of polytwistane using line symmetry group theory

Abstract

The electronic and mechanical properties of polytwistane are studied considering helical symmetry for the first time. All presented calculations were carried out using the density functional theory (DFT) and LCAO approach as implemented in the CRYSTAL17 code. It was found that the curve of the formation energy dependence on the rotation angle has only one minimum corresponding to the incommensurate structure (structure without translational symmetry). Symmetry cell (CH) and topological monomer (C6H6) were used for the calculations. It was found that changing the symcell from CH to C6H6 has effect only under extreme torsion. For the polytwistane structure corresponding to the energy minimum, the electronic band gap and mechanical properties were calculated. The results obtained for Young's moduli and band gap indicate a smooth change in these properties in relatively small ranges upon torsion and axial deformation of the structure.