Eur. Phys. J. B (2018) 91: 165
https://doi.org/10.1140/epjb/e2018-90141-6

Regular Article

Ab initio study of the (2 × 2) phase of barium on graphene^★

¹ Department of Physical and Chemical Sciences, University of L’Aquila, Via Vetoio 10, 67100 L’Aquila, Italy
² SPIN-CNR, University of L’Aquila, Via Vetoio 10, 67100 L’Aquila, Italy
³ Sorbonne Université, Institut des Nanosciences de Paris, UMR7588, 75252 Paris, France
⁴ Faculty of Physics, University of Vienna, Strudlhofgasse 4, 1090 Vienna, Austria
⁵ II. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, 50937 Cologne, Germany
⁶ Department of Materials Science, Moscow State University, Leninskiye Gory 1/3, 119992 Moscow, Russia

^a e-mail: gianni.profeta@aquila.infn.it

Received: 8 March 2018
Received in final form: 25 May 2018
Published online: 16 July 2018

Abstract

We present a first-principles density functional theory study on the structural, electronic and dynamical properties of a novel barium doped graphene phase. Low energy electron diffraction of barium doped graphene presents clear evidence of (2 × 2) spots induced by barium adatoms with BaC₈ stoichiometry. First principles calculations reveals that the phase is thermodynamically stable but unstable to segregation towards the competitive BaC₆ monolayer phase. The calculation of phonon spectrum confirms the dynamical stability of the BaC₈ phase indicating its metastability, probably stabilized by doping and strain conditions due to the substrate. Barium induces a relevant doping of the graphene π states and new barium-derived hole Fermi surface at the M-point of the (2 × 2) Brillouin zone. In view of possible superconducting phase induced by foreign dopants in graphene, we studied the electron–phonon coupling of this novel (2 × 2) obtaining λ = 0.26, which excludes the stabilization of a superconducting phase.