FORMATION OF A NOVEL DIAMOND-LIKE BILAYER BASED ON 5-7 GRAPHENE

Abstract

First-principle calculations of the structure and properties of orthorhombic L5-7 graphene and a novel diamond-like bilayer formed on its basis are performed. The calculations using the density functional theory method showed that L5-7 graphene of Stone-Wales defects should exist stably under normal conditions, and its structure should be corrugated in a wave-like manner. Under strong uniaxial compression of bilayer L5-7 graphene, the formation of the novel diamond-like DL5-7 bilayer can occur. The pressure of the « L5-7→DL5-7 » phase transition is 10,1 GPa, when the interlayer distance in bilayer graphene decreases to 1,61 Å. This bilayer has an orthorhombic crystal lattice (pbam) with the parameters a=10,145 Å and b=5,270 Å. The unit cell of the DL5-7 pbam bilayer contains 32 carbon atoms. The bond lengths vary in the range from 1,5590 to 1,6226 Å, while the angles between these bonds range from 89,62 to 140,8°. The structure of the diamond-like bilayer should be stable up to 270 K. The calculated values of the surface density and the difference total energy of this bilayer relative to the diamond total energy are 1,19·10^(-5) g/cm2 and 1,31 eV/atom, respectively. The DL5-7 pbam bilayer should be a semiconductor with a straight bandgap of 1,63 eV.

Keywords

• graphene
• topological defects
• diamond-like layer
• ab initio calculations
• crystal structure