Electron energy loss spectrum of graphane from first-principles calculations.

In this study, the energy loss near edge structure (ELNES) of carbon atoms in chair and tricycle conformers of hydrogenated graphene, namely 'graphane', has been calculated in the density functional theory using FP-LAPW method, and then, it has been compared with that of graphite and graphene. Using ELNES from chair conformer, the carbon K-edge was found to have a few main features including electron transition from 1s orbital of carbon atom to π*, σ*, and a hybridization of these two states. The first feature in tricycle conformer, however, has contributions of both π* and σ* states. The comparison of ELNES and the unoccupied density of states in each structure also justifies this. The energy difference between π* and σ* features of graphane conformers was decreased relative to it in graphite and graphene. Since the inclusion of core-holes and super-cells is essential for accurate reproduction of features in graphite and graphene, it may be essential as well for the ELNES spectra of graphane conformers.