Adsorption and decomposition mechanism of hexogen (RDX) on Al(111) surface by periodic DFT calculations.

The adsorption of hexogen (RDX) molecule on the Al(111) surface was investigated by the generalized gradient approximation (GGA) of density functional theory (DFT). The calculations employ a supercell (4×4×3) slab model and three-dimensional periodic boundary conditions. The strong attractive forces between RDX molecule and aluminum atoms induce the N-O and N-N bond breaking of the RDX. Subsequently, the dissociated oxygen atoms, NO₂ group and radical fragment of RDX oxidize the Al surface. The largest adsorption energy is -835.7 kJ mol(-1). We also investigated the adsorption and decomposition mechanism of RDX molecule on the Al(111) surface. The activation energy for the dissociation steps of V4 configuration is as large as 353.1 kJ mol(-1), while activation energies of other configurations are much smaller, in the range of 70.5-202.9 kJ mol(-1). The N-O is even easier than the N-NO2 bond to decompose on the Al(111) surface.