The interaction of beryllium with benzene and graphene: a comparative investigation based on DFT, MP2, CCSD(T), CAS-SCF and CAS-PT2.

The interaction of beryllium with benzene, graphene and graphitic compounds involves multi-reference electronic states, Jahn-Teller distortion, charge transfer and van der Waals interactions. This is investigated herein using periodic and molecular models at different levels of theory: (i) the second-order Møller-Plesset (MP2) perturbation theory, (ii) the coupled cluster method with inclusion of single double and perturbative triple excitations (CCSD(T)), (iii) the complete active space self-consistent field (CAS-SCF) and (iv) the complete active space with perturbation theory truncated at the 2nd order (CAS-PT2). Molecular and periodic Density Functional Theory (DFT) methods are also used. The two major failures of DFT are addressed with regard to the beryllium benzene and graphene interaction: the degeneracy problem is the source of no specific problem while the delocalization error causes DFT with the Perdew Burke, Ernzerhof functional plus the Grimme correction (DFT/PBE-D2) to be over-binding by about 0.4 eV at a short-range. The agreement between DFT/PBE-D2 and wave-function based methods is nevertheless good; DFT/PBE-D2 provides an accurate description of the electronic structure of the system. By the end of this work, we shall get a better insight into the mechanisms leading beryllium to physisorb on graphene and to chemisorb into the bilayer of graphite.

Adsorption of beryllium atoms and clusters both on graphene and in a bilayer of graphite investigated by DFT.

We herein investigate the interaction of beryllium with a graphene sheet and in a bilayer of graphite by means of periodic DFT calculations. In all cases, we find the beryllium atoms to be more weakly bonded on graphene than in the bilayer. Be(2) forms both magnetic and non-magnetic structures on graphene depending on the geometrical configuration of adsorption. We find that the stability of the Be/bilayer system increases with the size of the beryllium clusters inserted into the bilayer of graphite. We also find a charge transfer from beryllium to the graphite layers. All these results are analysed in terms of electronic structure.

Experimental and theoretical investigation of HC5N adsorption on amorphous ice surface: simulation of the interstellar chemistry.

HC 5N adsorbed on amorphous water ice at 10 K presents an interaction with the ice surface and induces the restructuring of the ice amorphous bulk. Warming up the sample induces the HC 5N desorption from the H 2O ice film, between 120 and 160 K, and the associated desorption energy is 90 kJ/mol. This value is in good agreement with that calculated E d (80 kJ/mol) and gives evidence that the amorphous ice surface is essentially dynamic. From theoretical calculations, it is shown that the HC 5N moiety presents a curvature and is no more linear and stabilized by two strong N...H bonds (2.09 and 2.29 A) and one H...O bond (1.84 A).