A DFT study of adsorption and decomposition of hexahydro-1,3,5-trinitro-1,3,5-triazine on Mg(0001) surface.

The adsorption and decomposition of hexogen (RDX) molecule on the Mg(0001) surface were investigated by the generalized gradient approximation (GGA) of density functional theory (DFT). The calculations employed a supercell (4 × 4 × 4) slab model and three-dimensional periodic boundary conditions. The strong attractive forces between RDX molecule and magnesium atoms induce the RDX's N - O bond breaking. Subsequently, the dissociated oxygen atoms and radical fragment of RDX oxidize the Mg surface. The largest adsorption energy is -2104.0 kJ mol(-1). We also investigated the decomposition mechanism of RDX molecule on the Mg(0001) surface. The activation energy for the dissociation step of configuration V4 is as small as 2.5 kJ mol(-1), while activation energies of other configurations are much larger, in the range of 964.9-1375.1 kJ mol(-1). Mg powder is more active than Al powder, and Mg powder performs better in increasing the combustion exothermicity of RDX as well.