Hydrogen-bonded cluster of nitroxyl: many-body analysis and spectroscopic characterization

Hydrogen bonding interactions in linear and cyclic clusters of nitroxyl are studied using density functional theory at PBEPBE/aug-cc-pvdz level. Many-body analysis technique is used to study the nature and strength of interactions in dimer, trimer, and tetramer of nitroxyl clusters. The vibrational and electronic absorption spectra are also obtained. Calculated geometrical parameters and vibrational frequencies of nitroxyl monomer at PBEPBE/aug-cc-pvdz level are in agreement with the experimental determinations. Significant shift in vibrational frequencies and change in their intensities is observed as we go from monomer to tetramer. Wavelength of electronic transition, oscillator strength, and HOMO to LUMO gap for the nitroxyl clusters are reported from electronic absorption spectra obtained using time-dependent density functional theory. Many-body analysis shows that two-, three-, and four-body energies have significant contribution to the binding energy of nitroxyl tetramers.