title: Solid-state modeling of the terahertz spectrum of the high explosive HMX.
abstract: The experimental solid-state terahertz (THz) spectrum (3-120 cm(-1)) of the beta-crystal form of the high explosive octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) has been analyzed using solid-state density functional theory calculations. Various density functionals (both generalized gradient approximation and local density approximation) are compared in terms of their abilities to reproduce the experimentally observed solid-state structure and low-frequency vibrational motions. Good-to-excellent agreement between solid-state theory and experiment can be achieved in the THz region where isolated-molecule calculations fail to reproduce the observed spectral features, demonstrating a clear limitation of using isolated-molecule calculations for the assignment of THz frequency motions in molecular solids. The deficiency of isolated-molecule calculations is traced to modification of the molecular structure in the solid state through crystal packing effects and the formation of weak C-H...O hydrogen bonds.
authors.affiliation: 1-014 Center for Science and Technology, Syracuse University, Syracuse, New York 13244, USA.
authors.forename: Damian G
authors.initials: DG
authors.lastname: Allis
authors.forename: Darya A
authors.initials: DA
authors.lastname: Prokhorova
authors.forename: Timothy M
authors.initials: TM
authors.lastname: Korter
mesh_terms: D001392:Azocines / Q000737:chemistry*; D003460:Crystallization; D053834:Explosive Agents / Q000737:chemistry*; D006573:Heterocyclic Compounds, 1-Ring / Q000737:chemistry*; D006860:Hydrogen Bonding; D008958:Models, Molecular; D015394:Molecular Structure; D013057:Spectrum Analysis; D014732:Vibration
chemical_list: D001392:Azocines; D053834:Explosive Agents; D006573:Heterocyclic Compounds, 1-Ring; C007950:octogen