Can the Optical Properties of Graphene be Modeled through a Classical Atomistic Approach? Tommaso Giovannini ⊤ , † Luca Bonatti ⊤ , ‡ Marco Polini, ¶,§ and Chiara Cappelli ∗,‡ †Department of Chemistry, Norwegian University of Science and Technology, 7491 Trondheim, Norway ‡Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa, Italy. ¶Dipartimento di Fisica dell’Universit´ a di Pisa, Largo Bruno Pontecorvo 3, I-56127 Pisa, Italy §Istituto Italiano di Tecnologia, Graphene Labs, Via Morego 30, 16163 Genova, Italy E-mail: chiara.cappelli@sns.it ⊤ T.G. and L.B. contributed equally to this work. Abstract We demonstrate that the optical properties of realistic graphene and graphene- based materials can effectively be modeled by a novel, fully atomistic, yet classical, approach, named ωFQ. Such model is able to reproduce all plasmonic features of these materials, and their dependence on shape, dimension and fundamental physical param- eters (Fermi energy, relaxation time and two-dimensional electron density). Remark- ably, ωFQ is able to accurately reproduce experimental data for realistic structures of hundreds of nanometers (∼ 370.000 atoms), which cannot be afforded by any ab-initio method. Also, the atomistic nature of ωFQ permits the investigation of complex shapes, which can hardly be dealt with by exploiting widespread continuum approaches. 1 arXiv:2004.09851v1 [cond-mat.mes-hall] 21 Apr 2020