ISOTHERMAL-ISOBARIC MOLECULAR-DYNAMICS SIMULATIONS OF 1,3,5,7-TETRANITRO-1,3,5,7-TETRAAZACYCLOOCTANE (HMX) CRYSTALS

Isothermal-isobaric molecular dynamics (NPT-MD) simulations of the bet a, alpha, and delta phases of crystalline 1,3,5,7-tetranitro-1,3,5,7-t etraazacyclooctane (HMX) were performed over the temperature range 4.2 -553 K and 1 arm. The Buckingham repulsion-dispersion intermolecular p otential developed for hexahydro-1,3,5-trinitro-1,3,5-s-triazine (RDX) (J. Phys. Chem. 1997, B101, 798) with electrostatic charges determine d by ab initio calculations was used to describe the HMX crystal phase s. The predicted space group symmetries and structural parameters for the three phases of HMX are in close agreement with experimental value s.