Structure and Bonding in β-HMX-Characterization of a Trans-Annular N···N Interaction

Chemical bonding in the β-phase of the 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (HMX) crystal based on the experimental electron density obtained from X-ray diffraction data at 20 K, and solid state theoretical calculations, has been analyzed in terms of the quantum theory of atoms in molecules. Features of the intra- and intermolecular bond critical points and the oxygen atom lone-pair locations are discussed. An unusual N···N bonding interaction across the 8-membered ring has been discovered and characterized. Hydrogen bonding, O···O and O···C intermolecular interactions are reported. Atomic charges and features of the electrostatic potential are discussed.