Ab initio study of interlayer interaction of graphite: Benzene-coronene and coronene dimer two-layer models

A study was made of a series of one-layer and two-layer models of graphite surface and especially of interactions in the two-layer models. Seven one-l ayer models, of increasing size up to seven rings, in the C6n2H6n series we re calculated for reference purposes with the Hartree-Fock method. Four two -layer models with different stacking sequences (AA, ABAB, and ABCABC) were studied with second-order Moller-Plesset perturbation method using basis s et 6-31G*, and one model (ABAB) was also studied with 6-311G* and 6-311G** basis sets. Properties such as charge distribution and density of energy st ates were compared for the different models. Optimal interlayer distance fo r (C24H12)(2) with MP2 method and 6-31G* basis was 3.41 Angstrom and for th e three C24H12-C6H6 models of different stacking sequence about 3.5 Angstro m, which agrees fairly well with the experimental value of 3.35 Angstrom. T he BSSE corrected MP2 interaction energy for (C24H12)(2) was -78.1 kJ/mol, whereas interaction energies for the three C24H12-C6H6 models were in the r ange of -21.8 to -22.8 kJ/mol. The bigger basis set 6-311G** gave almost tw ice as strong an interaction for ABAB, -38.8 kJ/mol, as did the 6-31G* basi s set. Optimal interlayer distances for ABAB model were 3.29 Angstrom with 6-311G* and 6-311G* basis sets.