High-level ab initio investigations on structures and energetics of N2O clusters.

Both experimental and theoretical investigations on weakly bonded small N2O clusters have been a subject of interest for the past decade. The current article presents high-level ab initio calculations for (N2O)n clusters for n = 4-6 employing second-order Møller-Plesset (MP2) theory and coupled cluster singles and doubles with perturbative triple (CCSD(T)) theory using Dunning's correlation-consistent basis sets. The electrostatics-guided cluster building code developed in our laboratory is applied for the generation of initial cluster geometries, followed by geometry optimization at MP2/aug-cc-pVTZ level of theory. Calculations of single point energy at CCSD(T)/aug-cc-pVTZ and vibrational frequency at the MP2/aug-cc-pVTZ level of theory are facilitated by the fragment-based molecular tailoring approach (MTA). A comparison of the results is done with those obtained by employing dispersion-corrected density functional B2PLYPD with aug-cc-pVTZ basis set. The geometrical parameters and vibrational spectra obtained from these ab initio methods are found to be in good agreement with those derived from recent experimental findings of Oliaee et al. [J. Chem. Phys. 2011, 134, 074310] and Rezaei et al. [J. Chem. Phys. 2012, 136, 224308].