Nuclear fukui functions and the deformed atoms in molecules representation of the electron density: Application to gas‐Phase RDX (hexahydro‐1,3,5‐trinitro‐1,3,5‐ triazine) electronic structure and decomposition

Abstract

ABSTRACT:The electronic structure and the onset of decomposition processes of the four conformers of the RDX molecule were studied through the density functional theory (DFT) along with the B3LYP functional and the 6-311þG(2d,p) Gaussian basis set. The computed DFT electron density was decomposed into atomic contributions using the deformed atoms in molecules (DAM) method, which allowed us to identify regions of electron accumulation and electron depletion of each conformer. The nuclear Fukui functions nuclear stiffness and nuclear reactivity index were then calculated. Both functions are atomic vectors, intrinsic molecular properties, which provide information for the onset of the fragmentation process, were further discussed through the analysis of the DAM electron density. The computed, decomposed electronic structures indicate that equatorial (E) NO 2 (nitro) groups are less bulky than axial (A) groups, with the Additional Supporting Information may be found in the online version of this article. former contributing more than the latter to the increase of the ring delocalized electrons and, therefore, to the lower stability of conformers with more E groups. Concerning the decomposition, the RDX NANO 2 bond cleavage is the most probable process for the AAA, AEE, and EEE conformers, while for the AAE conformer, HONO elimination is favored in partial agreement with previous study.

Predicting Trigger Bonds in Explosive Materials through Wiberg Bond Index Analysis

“…Increases in N(sp 3 )−NO 2 bond lengths in RDX, in general, could be attributed to the substitution with increased repulsion between the multiple nitro groups. In particular, axial N(sp 3 )−NO 2 bonds are longer and weaker with each additional equatorial nitro group due to more delocalization to the ring backbone, such that the C(sp 3 )−N(sp 3 ) bonds are strengthened (%ΔWBI=+1.76 % relative to DMNA) at the expense of the axial N(sp 3 )−NO 2 bonds which are the most likely trigger bonds, consistent with previous theoretical and experimental results …”

Trigger bond analysis of nitroaromatic energetic materials using wiberg bond indices

“…Although many factors unique to the solid state can influence the sensitivity of energetic materials, gas‐phase calculations can contribute to understanding how intramolecular interactions influence sensitivity. Theoretical measures of bond strength include the Atoms‐In‐Molecules (AIM) method, unimolecular decomposition activation barriers, bond dissociation energies (BDEs) and Mulliken population analysis . Our group has recently examined the use of the Wiberg bond index (WBI) analysis as an efficient method for assigning trigger bonds.…”

On the molecular origin of the sensitivity to impact of cyclic nitramines

“…Our efforts on this subject have been inspired especially by the aforementioned works of Politzer, Murray, and Rice. In another direction in the search of greater understanding of energetic molecules, electronic excited states have also been investigated …”