title: Charge-density studies of energetic materials: CL-20 and FOX-7.
abstract: Experimental electron densities and derived properties have been determined for the two energetic materials CL-20 (3,5,9,11-tetraacetyl-14-oxo-1,3,5,7,9,11-hexaazapentacyclo-[5.5.3.02,6.04,10.08,12]pentadecane), and FOX-7 (1,1-diamino-2,2-dinitroethylene) from single-crystal diffraction. Synchrotron data extending to high scattering angles were measured at low temperature. Low figures-of-merit and excellent residuals were obtained. The Hansen & Coppens multipole-model electron density was compared with results from theoretical calculations via structure factors simulating an experiment. Chemical bonding in the molecules is discussed and a topological analysis gives insight especially into the character of those bonds that are thought to play a key role in the decomposition of the molecules. A comparison of theoretical and experimental electrostatic potentials shows no obvious evidence supporting earlier findings on other nitroheterocyclic molecules that electron-density maxima near the C-NO(2) bonds mapped on the electron-density isosurface can be correlated with impact sensitivities. For FOX-7 periodic Hartree-Fock calculations were performed to investigate the influence of the crystal field on the electron density distribution.
authors.affiliation: HASYLAB at DESY, Notkestrasse 85, D-22607 Hamburg, Germany. alke.meents@desy.de
authors.forename: A
authors.initials: A
authors.lastname: Meents
authors.forename: B
authors.initials: B
authors.lastname: Dittrich
authors.forename: S K J
authors.initials: SK
authors.lastname: Johnas
authors.forename: V
authors.initials: V
authors.lastname: Thome
authors.forename: E F
authors.initials: EF
authors.lastname: Weckert
mesh_terms: D001372:Aza Compounds / Q000737:chemistry*; D018360:Crystallography, X-Ray; D005030:Ethylenes / Q000737:chemistry*; D006571:Heterocyclic Compounds / Q000737:chemistry*; D008958:Models, Molecular; D009574:Nitro Compounds / Q000737:chemistry*
chemical_list: C520681:1,1-diamino-2,2-dinitroethylene; C482139:2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaaza-isowurtzitane; D001372:Aza Compounds; D005030:Ethylenes; D006571:Heterocyclic Compounds; D009574:Nitro Compounds