Accurate structures and rotational constants of nitroaromatic explosives and their taggants at DFT cost by Pisa composite schemes and vibrational perturbation theory

Abstract

The structures and rotational constants of representative nitroaromatic explosives and their taggants have been analyzed combining composite quantum chemical schemes and second order vibrational perturbation theory. The vibrational corrections obtained by a hybrid density functional together with the equilibrium geometries calculated by explicitly correlated wave function methods or double hybrid functionals show average deviations of around 0. 1% from the experimental rotational constants, which correspond to errors of approximately 1 mÅ for bond lengths and 0.1 degrees for valence angles. Beyond the intrinsic interest of the molecules investigated, this work confirms that spectroscopic analyses of large systems can now benefit from an accurate, low-cost computational tool.