Periodic Dispersion-Corrected Approach for Isolation Spectroscopy of N 2 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 N ₂ -Ar _n (n ≤ 3) complexes and N ₂ trapped in Ar matrix (i.e., N ₂ @Ar). For cluster computations, we used both Møller-Plesset (MP2) and PBE-D3 methods. For N ₂ @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 N ₂ interacting with these entities. We also deduced the N ₂ vibrational frequency shifts caused by clustering or embedding compared to an isolated N ₂ molecule. Upon complexation or embedding, the vibrational frequency of N ₂ is slightly shifted, while its equilibrium distance remains unchanged. This is due to the weak interactions between N ₂ 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 N ₂ isolated, in interaction with Ar surfaces, or trapped in Ar matrices.