INQUISUR   21779
INSTITUTO DE QUIMICA DEL SUR
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Adsorption of Al on Graphene: DFT and MP2 calculations
Autor/es:
N.F. DOMANCICH; N.J. CASTELLANI; R.M. FERULLO
Lugar:
Santiago
Reunión:
Congreso; 10th. Congress of the World Association of Theoretical and Computational Chemists; 2014
Institución organizadora:
Pontificia Universidad Católica de Chile
Resumen:
The study of the interaction of a non-transition metal atom with graphene is relevant from a fundamental point of view because only s-p orbitals of adsorbate are implied. Density functional theory (DFT) calculations for Li/graphene based on Perdew-Becke-Enrzerhof (PBE) [1] or Becke, three-parameter, Lee-Yang-Parr (B3LYP) [2] functionals pointed out the presence of a chemisorption process with an electron transfer from the adsorbate to the graphene. In these two approaches the reaction is exothermic. On the other hand, calculations performed within the second order Møller?Plesset (MP2) perturbation formalism [3] support the existence of exothermic states of physisorption nature at adsorbate-substrate distances of about 3 Å while at shorter distances of about 2 Å only endothermic states are produced. In the present work, molecular orbital calculations using a cluster model were performed within DFT with the PBE and B3LYP functionals and restricted open MP2 (ROMP2) in order to study the adsorption of an Al atom on regular graphene. For that purpose, the sites of adsorption were simulated as the central 1-fold, 2-fold and 6-fold sites at the center of the circumcoronene molecule (C54H18). In all the calculations the 6-31G** basis set was used. The PBE functional shows that weak chemisorption is produced at Al-graphene distances of 2.1-2.3 Å for the three adsorption sites, with Eads values of about -0.3 to -0.4 eV. Conversely, the results obtained with the B3LYP functional exhibit that the Al-graphene reaction is endothermic for hollow and bridge sites, with adsorption energies about 0.1 eV, presenting somewhat larger Al-graphene distances, c. 0.05-0.08 Å; moreover, no bonding is present on the on-top site. The addition of van der Waals corrections to these results show that PBE functional gives deeper exothermic adsorption processes while the B3LYP functional gives exothermic adsorption of about -0.2 to -0.3 eV for the three sites. At distances of about 3.0 Å only defined physisorption processes have been found with B3LYP for the hollow and bridge sites. The calculations performed at the ROMP2 level show two geometric situations, at about 2.1-2.2 Å and about 3.0 Å, both with adsorption energies of -0.3 to -0.5 eV.