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(a) Schematic representation of the atomic structure of graphene and graphane. (b) rectangular supercell configuration of the system containing 128 C-H pairs used for the calculation of the elastic constants. and are the lattice constants of the supercell in - and -directions. Shaded region is the smallest unit cell. (c) The mesh of data points used for the total energy calculations. The units are given in angstroms. (d) The three-dimensional plot of and corresponding total energy values. The red balls are actual points and the lines are the fitted formula.
2D graphane under uniform expansion. (a) Initial atomic configuration in a supercell treated with periodic boundary condition. (b) The variation in strain energy and its derivative. The orange/shaded region indicating the plastic range. Strains corresponding to two critical points in the elastic range are labeled as and . (c) Similar to (b) for a single H-vacancy in a supercell. (d) For -divacancy in a supercell.
The variation in energy band gaps with (2D) uniform expansion. The band gaps obtained both from GGA (green triangles) and (blue squares) calculations increase with increasing strain up to , passes through a maximum, then decrease until the yielding point. The band gaps are given on the left and the strain energies are given on the right. Three panels show how the bands at the edge of conduction band are modified with strain.
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