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

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 6-311+G(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) NO2 (nitro) groups are less bulky than axial (A) groups, with the 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 N-NO2 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. (C) 2010 Wiley Periodicals, Inc. Int J Quantum Chem 111: 1444-1452, 2011