Bromination of Graphene and Graphite
  We present a density functional theory study of low density bromination of graphene and graphite, finding significantly different behaviour in these two materials. On graphene we find a new Br2 form where the molecule sits perpendicular to the graphene sheet with an extremely strong molecular dipole. The resultant Br+-Br- has an empty pz-orbital located in the graphene electronic pi-cloud. Bromination opens a small (86meV) band gap and strongly dopes the graphene. In contrast, in graphite we find Br2 is most stable parallel to the carbon layers with a slightly weaker associated charge transfer and no molecular dipole. We identify a minimum stable Br2 concentration in graphite, finding low density bromination to be endothermic. Graphene may be a useful substrate for stabilising normally unstable transient molecular states. 
A. Yaya, C. P. Ewels, I. Suarez-Martinez, Ph. Wagner, S. Lefrant, A.   Okotrub, L. Bulusheva, P. R. Briddon
cond-mat.mes-hall cond-mat.mtrl-sci