Multi-scale theoretical investigation of molecular hydrogen adsorption over graphene: coronene as a case study
The physisorption of molecular hydrogen onto coronene is studied using a multi-scale theoretical approach with Density Functional Theory (DFT) calculations and Molecular Dynamics (MD) simulations. We consider two different kinds of model conformation for the approach of hydrogen towards the coronene i.e., systematic and random. For the systematic attack of hydrogen over coronene, the resulting potential energy profiles from DFT analysis are further found to resemble the Morse potential, and even the highly flexible Murrell–Sorbie (M–S) potential. The resulting M–S fitting also shows a zero-point energy correction of ∼16–17%. On the other hand, the potential energies from the random approach have been implemented into the Improved Lennard-Jones (ILJ) force field of the DL_POLY package following a prior statistical treatment. The MD simulations have been performed at different temperatures from 10 to 390 K. For the interaction of seven hydrogen molecules with coronene, the DFT method shows an average interaction energy of −3.85 kJ mol−1 per H2, which is slightly smaller than the Coupled Cluster value (CCSD(T)) of −4.71 kJ mol−1 that was calculated for a single molecule in the most favorable situation. Moreover, the MD calculations reveal a mean interaction energy of −3.69 kJ mol−1 per H2 (a gross mean Ecfg of −25.98 kJ mol−1 at T = 299.97 K), which is again in good agreement with the aforementioned DFT results, proving the quality of the approach used for the study of van der Waals interactions between hydrogen and graphene.