Effects of hydrogen to the graphene and graphene vacancy are reanalyzed by investigating the electronic structures and charge distribution. Recently, a systematic creation method to fabricate a hydrogenated grapahene vacancy was invented by Ziatodinov et al [1] & Kudo et al [2]. Following the technique, we make model of hydrogenated graphene and hydrogenated graphene vacancy in order to get deeper understanding regarding the effect of hydrogenation process on graphene and graphene vacancy.
We have applied Löwdin analysis in the density functional theory framework. The simulation have been done using VASP code [3] and Quantum Espresso code [4]. Several structures were prepared in a super-cell, i.e. graphene consisting of 24 carbon atoms and hydrogen atoms to represent hydrogenated graphene and graphene consisting of 63 carbon atoms and hydrogen atoms to represent hydrogenated grapahene vacancy. The Fermi level of hydrogenated graphene is shifted upward because of electrons doped from hydrogen to graphene and there is sharp peak close to the Fermi level coming from pz orbital. As for hydrogenated graphene vacancy, there is large density of states at the Fermi level coming from localized states caused by the vacancy. The number of transferred electrons from a hydrogen atom was around 0.2e per hydrogen adsorbed, and 0.5e per a vacancy, which was approximately comparable with experimental result by Kudo et al [2].