Comparative investigation of pure and mixed rare gas atoms on coronene molecules

Abstract

Clusters formed by the combination of rare gas (RG) atoms of He, Ne, Ar, and Kr on coronene have been investigated by means of a basin-hopping algorithm and path integral Monte Carlo calculations at T = 2 K. Energies and geometries have been obtained and the role played by the specific RG-RG and RG-coronene interactions on the final results is analysed in detail. Signatures of diffuse behavior of the He atoms on the surface of the coronene are in contrast with the localization of the heavier species, Ar and Kr. The observed coexistence of various geometries for Ne suggests the motion of the RG atoms on the multi-well potential energy surface landscape offered by the coronene. Therefore, the investigation of different clusters enables a comparative analysis of localized versus non-localized features. Mixed Ar-He-coronene clusters have also been considered and the competition of the RG atoms to occupy the docking sites on the molecule is discussed. All the obtained information is crucial to assess the behavior of coronene, a prototypical polycyclic aromatic hydrocarbon clustering with RG atoms at a temperature close to that of interstellar medium, which arises from the critical balance of the interactions involved.

Adsorption of molecular hydrogen on coronene with a new potential energy surface

“…For N = 13, the seven units of H 2 on one side of the coronene are close to occupy localized top positions above the C atoms of the outer ring. As seen in our previous paper on RG atoms on coronene 34 the precise location is driven by the equilibrium distance between consecutive H 2 molecules, a feature which seems to explain why the hollow sites are not occupied in this case.…”

“…Regarding the energetics and structures of the (H 2 ) N -coronene clusters, present results can be compared with previous studies on different RG-doped coronene clusters 34,36 . For instance, the BH minimum structures shown in Fig.…”

“…The PIMC approach was already explained in previous publications 34,36 and therefore we will simply present the numerical details of the calculation. The total HamiltonianĤ can be written…”

“…where M is the number of beads considered in the calculation once the total density matrix at temperature T is assumed fractioned in M density matrices at higher temperatures MT 34,36 ;…”

“…In a series of previous papers, we treated coronene clusters doped with RG atoms [34][35][36] , such as He, Ne, Ar and Kr. Energies and structures of (RG) N -coronene systems (including also combinations of different RG atoms) were calculated by means of basinhopping (BH) and path integral Monte Carlo (PIMC) calculations employing a PES developed by some of us 37 .…”