Interaction of aluminum with graphene: DFT study of adsorption and insertion processes

NICOLAS DOMANCICH; MARIA MARTA BRANDA; RICARDO M. FERULLO; NORBERTO J. CASTELLANI

Granada

Congreso; XXXIX Congreso Internacional de Químicos Teóricos de Expresión Latina (QUITEL); 2013

Universidad de Granada

In the present work density functional theory (DFT) calculations were performed to study the adsorption of an Al atom on regular sites and on a C vacancy of graphene using the Gaussian 03 code. The surface was model using the cluster model approach. Depending on the theoretical treatment of electronic exchange and correlations effects, different results for the adsorption on regular sites are obtained. On the other hand, these approximations give very similar results for the adsorption on the monovacancy. On regular graphene, the adsorption resulted to be exothermic (by about -0.3 eV) when the PBE functional is used and endothermic (by about 0.1eV) with B3LYP. Calculations carried out at MP2 level reveal that at distances of about 2.2 Å a significant repulsion is present, producing metastable adsorbed states for on-top and hollow sites. Furthermore, at large distances (of about 3 Å) dispersive forces allow the appearance of adsorbed states, not predicted by standard DFT, favored by about 0.2 eV. The formation of a carbon vacancy in a graphene sheet is similarly described with both functionals. This process demands about 15.5 eV and is accompanied with the lost of trigonal symmetry. The carbon atoms of concave angles in the vacancy are the most reactive to a radical attack according to their condensed Fukui function. The adsorption of an Al atom on the vacancy restores the trigonal symmetry. Complementary calculations performed using the slab model and the PBE functional as implemented in the VASP code support the results obtained with the cluster model, arriving to similar geometries and attaining Eads values comparable with other reported results.