Theoretical spectroscopy techniques applied to graphene EELS and optics
  A thorough understanding of the electronic structure is a necessary first step for the design of nanoelectronics, chemical/bio-sensors, electrocatalysts, and nanoplasmonics using graphene. As such, theoretical spectroscopic techniques to describe both direct optical excitations and collective excitations of graphene are of fundamental importance. Starting from density functional theory (DFT) we use the time dependent linear response within the random phase approximation (TDDFT-RPA) to describe the loss function -Im{{\epsilon}\overline{ }^{1}(q,{\omega})} for graphene. To ensure any spurious interactions between layers are neglected, we employ both a radial cutoff of the Coulomb kernel, and extra vacuum directly at the TDDFT-RPA level. 
D. J. Mowbray, P. Ayala, V. Despoja, T. Pichler, and A. Rubio
cond-mat.mtrl-sci