Computer simulation of crystals formed from 4-6-12 and 5-7 fluorographene layers

Abstract

The three-dimensional structure of four fluorographene crystals was calculated by the atom-atom potential method. The crystals consisted of 4-6-12 or 5-7 graphene layers functionalized by fluorine packed in stacks. The structure of fluorographene layers of two polymorphs T1 and T3 for 4-6-12 layer and two polymorphs of 5-7 layer T1 and T2 was considered. The electronic structure was calculated by the density functional theory method in the generalized gradient approximation. As a result of the calculations, it was established that the interlayer distances in various fluorographene crystals vary in the range from 5.4921 to 5.7645 Å. In CF-L4-6-12 T1 crystals, the relative shift of adjacent layers is close to zero. In the remaining fluorographene crystals, the layer shift vector varies from 0.336 to 0.3714 nm. The energy of interlayer bonds per atom is minimal for CF-L5-7 crystal of T2 type and is -3024.44 J/mol. The maximum value of the binding energy is equal to -2291.35 J/mol and observed in CF-L4-6-12 crystals of T3 type. The sublimation energy varies from 13.83 to 14.24 eV, and the band gap from 2.827 to 3.682 eV. The band gap in CF crystals is 0.2--0.4 eV less than in isolated fluorographene layers.