title: Intermolecular stabilization of 3,3'-diamino-4,4'-azoxyfurazan (DAAF) compressed to 20 GPa.
abstract: The room temperature stability of 3,3'-diamino-4,4'-azoxyfurazan (DAAF) has been investigated using synchrotron far-infrared, mid-infrared, Raman spectroscopy, and synchrotron X-ray diffraction (XRD) up to 20 GPa. The as-loaded DAAF samples exhibited subtle pressure-induced ordering phenomena (associated with positional disorder of the azoxy "O" atom) resulting in doubling of the a-axis, to form a superlattice similar to the low-temperature polymorph. Neither high pressure synchrotron XRD, nor high pressure infrared or Raman spectroscopies indicated the presence of structural phase transitions up to 20 GPa. Compression was accommodated in the unit cell by a reduction of the c-axis between the planar DAAF layers, distortion of the β-angle of the monoclinic lattice, and an increase in intermolecular hydrogen bonding. Changes in the ring and -NH2 deformation modes and increased intermolecular hydrogen bonding interactions with compression suggest molecular reorganizations and electronic transitions at ∼ 5 GPa and ∼ 10 GPa that are accompanied by a shifting of the absorption band edge into the visible. A fourth-order Birch-Murnaghan fit to the room temperature isotherm afforded an estimate of the zero-pressure isothermal bulk modulus, K0 = 12.4 ± 0.6 GPa and its pressure derivative K0' = 7.7 ± 0.3.
authors.affiliation: Lujan Center, MS H805, §Shock and Detonation Physics, MS P952, and ⊥Theoretical Division, Los Alamos National Laboratory , Los Alamos New Mexico 87545, United States.
authors.forename: Raja S
authors.initials: RS
authors.lastname: Chellappa
authors.forename: Dana M
authors.initials: DM
authors.lastname: Dattelbaum
authors.forename: Joshua D
authors.initials: JD
authors.lastname: Coe
authors.forename: Nenad
authors.initials: N
authors.lastname: Velisavljevic
authors.forename: Lewis L
authors.initials: LL
authors.lastname: Stevens
authors.forename: Zhenxian
authors.initials: Z
authors.lastname: Liu
mesh_terms: D006860:Hydrogen Bonding; D015394:Molecular Structure; D010069:Oxadiazoles / Q000737:chemistry*; D011312:Pressure; D013055:Spectrophotometry, Infrared; D013059:Spectrum Analysis, Raman; D013696:Temperature; D014732:Vibration; D014961:X-Ray Diffraction
chemical_list: D010069:Oxadiazoles