Equations of state of anhydrous AlF3 and AlI3: Modeling of extreme condition halide chemistry

Abstract

Pressure dependent angle-dispersive x-ray powder diffraction measurements of alpha-phase aluminum trifluoride (α-AlF3) and separately, aluminum triiodide (AlI3) were conducted using a diamond-anvil cell. Results at 295 K extend to 50 GPa. The equations of state of AlF3 and AlI3 were determined through refinements of collected x-ray diffraction patterns. The respective bulk moduli and corresponding pressure derivatives are reported for multiple orders of the Birch-Murnaghan (B-M), finite-strain (F-f), and higher pressure finite-strain (G-g) EOS analysis models. Aluminum trifluoride exhibits an apparent isostructural phase transition at approximately 12 GPa. Aluminum triiodide also undergoes a second-order atomic rearrangement: applied stress transformed a monoclinically distorted face centered cubic (fcc) structure into a standard fcc structural arrangement of iodine atoms. Results from semi-empirical thermochemical computations of energetic materials formulated with fluorine containing reactants were obtained with the aim of predicting the yield of halogenated products.

Thermal Atomic Layer Etching of Aluminum Oxide (Al2O3) Using Sequential Exposures of Niobium Pentafluoride (NbF5) and Carbon Tetrachloride (CCl4): A Combined Experimental and Density Functional Theory Study of the Etch Mechanism

“…According to Morelock et al, aluminum trifluoride adopts a cubic form above 440 °C, which upon cooling changes to a rhombohedral phase. The X-ray diffraction (XRD) analysis of about 11 nm AlF X [O] layer revealed the rhombohedral phase (see the Supporting Information S4) and is thus consistent with the literature. − On the contrary, at 400 °C, the thickness of the fluorinated layer stayed around 3 nm even after prolonged total NbF 5 exposure of 2700 s. Chen et al showed the fluoride ions penetrating up to 2 nm thick aluminum oxide after treating fluorinated alumina at 400 °C, and neutral/ion beams-assisted fluorination lead to a thicker AlF X [O] layer . Moreover, up to 0.5 nm thick AlF 3 layer was obtained at a lower temperature of 300 °C with HF as a fluorinating agent .…”

Intercalating Helium into A-Site Vacant Perovskites

“…Let us introduce the MX 3 perovskites we considered in this study, focusing on their structures and the geometric peculiarities of their important vacant A-sites where the helium atom may be stuffed. AlF 3 , GaF 3 , and InF 3 belong to the VF 3 -type materials family crystallizing in the R 3̅ c space group. , Experiments revealed this rhombohedral structure remains the ground state up to 50 GPa for AlF 3 and 28 GPa for GaF 3 . Comparison of the enthalpy calculated for R 3̅ c -AlF 3 with the enthalpies of other known stable and metastable polymorphs that can be made at high temperatures or using molecular templates , revealed that it was the preferred geometry at both 0 and 10 GPa (Table S4).…”

High-pressure phase transition of AB3-type compounds: case of tellurium trioxide

“…This polytype is more commonly encountered in triuorides. In this context, it is of interest to explore the high-pressure phase transformations of TeO 3 , and compare them with those of triuorides, [24][25][26] and trioxides, in particular, WO 3 , [27][28][29][30][31] and ReO 3 itself. [32][33][34][35] Here we present a combined experimental (Raman scattering) and theoretical (DFT modelling) study on the inuence of high pressure on the structure stability of TeO 3 .…”