Structure and redox properties of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) adsorbed on a silica surface. A DFT M05 computational study

Abstract

Adsorption of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) on (001) surface of α-quartzwas studiedat the M05/tzvp level using cluster approximation. Hydrogen bonds between nitramines and silica surface were analyzed by atoms in molecules (AIM) method. Electron attachment causes significant change in geometry of adsorbed complexes. Redox properties of adsorbed RDX and HMX were compared with those of gas-phase and hydrated species by calculation of the ionization potential, electron affinity, oxidation and reduction Gibbs free energies, oxidation and reduction potentials. Calculations show that adsorbed RDX and HMX have lower ability to undergo redox transformations than hydrated ones.

Keywords

• silica, RDX, HMX, adsorption, reduction, oxidation