Charge Density Distribution, Electrostatic Properties, and Impact Sensitivity of the High Energetic Molecule TNB: A Theoretical Charge Density Study

摘要

A quantum chemical calculation and a charge density analysis have been performed on the energetic molecule trinitrobenzene (TNB) to characterize its bond strength and to relate the bond topological parameters with the impact sensitivity. The optimized geometry of the molecule was calculated by the density functional method B3P86 with the basis set 6-311G**. The bond topological analysis predicts a significantly low bond electron density (~1770 e nm~(-3)) as well as Laplacian of electron density (—1.67 x 10~6 e nm~(-5)) for C—N bonds. This low value of the Laplacian indicates, the charges of these bonds are highly depleted, which confirms that these are the weakest bonds in the molecule. The N = O bonds bear a high negative value of Laplacian, reflecting that the bond charges are highly concentrated. The isosurface of the molecular, electrostatic potential (ESP) shows large electronegative regions at the vicinity of —NO2 groups. Further analysis of ESP in the bonding region allows predicting the impact sensitivity. A sound relationship has been found between the ESP at the mid point of the bonds and its bond charge depletion. The positive ESP at the mid points of highly charge depleted C—NO2 bonds reveals that these bonds are the sensitive bonds in the molecule.