Molecular versus atom–atom interaction anisotropy in the case of the Ar–N2 van der Waals system

Periodic Dispersion-Corrected Approach for Isolation Spectroscopy of N2 in an Argon Environment: Clusters, Surfaces, and Matrices

Ab initio and Perdew, Burke, and Ernzerhof (PBE) density functional theory with dispersion correction (PBE-D3) calculations are performed to study N₂-Ar_n (n ≤ 3) complexes and N₂ trapped in Ar matrix (i.e., N₂@Ar). For cluster computations, we used both Møller-Plesset (MP2) and PBE-D3 methods. For N₂@Ar, we used a periodic-dispersion corrected model for Ar matrix, which consists on a slab of four layers of Ar atoms. We determined the equilibrium structures and binding energies of N₂ interacting with these entities. We also deduced the N₂ vibrational frequency shifts caused by clustering or embedding compared to an isolated N₂ molecule. Upon complexation or embedding, the vibrational frequency of N₂ is slightly shifted, while its equilibrium distance remains unchanged. This is due to the weak interactions between N₂ and Ar within these compounds. Our calculations show the importance of inclusion of dispersion effects for the accurate description of geometrical and spectroscopic parameters of N₂ isolated, in interaction with Ar surfaces, or trapped in Ar matrices.