Determination of Equations of State for AlF3 and AlI3: Semi-empirical Modeling of Extreme Condition Halide Chemistry

Pressure dependent angle-dispersive x-ray powder diffraction measurements of alpha-phase aluminum trifluoride (alpha-AlF$_{\mathrm{3}})$ and separately, aluminum triiodide (AlI$_{\mathrm{3}})$ were conducted using a diamond-anvil cell. Results at 295 K extend to 50 GPa. The equations of state of AlF$_{\mathrm{3}}$ and AlI$_{\mathrm{3}}$ were determined through refinements of collected x-ray patterns. The respective bulk moduli and corresponding pressure derivatives using multiple orders of the Birch-Murngahan, Ff, and Gg EoS models will be discussed. Aluminum trifluoride exhibits no pressure induced structural phase transition while the triiodide data reveal a second-order iso-structural rearrangement: Applied stress transformed a monoclinicly distorted face centered cubic (FCC) structure into a perfect FCC structure. Results from semi-empirical thermochemical computations of energetic materials formulated with fluorine containing reactants will be presented. * This work was performed under the auspices of the U.S. Department of Energy jointly by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.