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AlF3 crystallizes in the trigonal R-3c space group. The structure is three-dimensional. Al3+ is bonded to six equivalent F1- atoms to form corner-sharing AlF6 octahedra. The corner-sharing octahedral tilt angles are 20°. All Al–F bond lengths are 1.82 Å. F1- is bonded in a bent 150 degrees geometry to two equivalent Al3+ atoms.
AlF3 crystallizes in the tetragonal P4/mbm space group. The structure is three-dimensional. there are two inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to six F1- atoms to form corner-sharing AlF6 octahedra. The corner-sharing octahedra tilt angles range from 0–32°. There are a spread of Al–F bond distances ranging from 1.80–1.85 Å. In the second Al3+ site, Al3+ is bonded to six F1- atoms to form corner-sharing AlF6 octahedra. The corner-sharing octahedra tilt angles range from 0–29°. There is four shorter (1.81 Å) and two longer (1.82 Å) Al–F bond length. There are five inequivalent F1- sites. In the first F1- site, F1- is bonded in a bent 150 degrees geometry to two Al3+ atoms. In the second F1- site, F1- is bonded in a linear geometry to two equivalent Al3+ atoms. In the third F1- site, F1- is bonded in a linear geometry to two equivalent Al3+ atoms. In the fourth F1- site, F1- is bonded in a bent 150 degrees geometry to two equivalent Al3+ atoms. In the fifth F1- site, F1- is bonded in a linear geometry to two equivalent Al3+ atoms.
AlF3 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. there are two inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to six F1- atoms to form corner-sharing AlF6 octahedra. The corner-sharing octahedra tilt angles range from 14–32°. All Al–F bond lengths are 1.82 Å. In the second Al3+ site, Al3+ is bonded to six F1- atoms to form corner-sharing AlF6 octahedra. The corner-sharing octahedra tilt angles range from 15–32°. All Al–F bond lengths are 1.82 Å. There are four inequivalent F1- sites. In the first F1- site, F1- is bonded in a linear geometry to two equivalent Al3+ atoms. In the second F1- site, F1- is bonded in a linear geometry to two equivalent Al3+ atoms. In the third F1- site, F1- is bonded in a bent 150 degrees geometry to two Al3+ atoms. In the fourth F1- site, F1- is bonded in a bent 150 degrees geometry to two equivalent Al3+ atoms.
AlF3 crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are two inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded in a 6-coordinate geometry to six F1- atoms. There are a spread of Al–F bond distances ranging from 1.78–2.24 Å. In the second Al3+ site, Al3+ is bonded to six F1- atoms to form corner-sharing AlF6 octahedra. The corner-sharing octahedral tilt angles are 11°. There are a spread of Al–F bond distances ranging from 1.73–1.88 Å. There are six inequivalent F1- sites. In the first F1- site, F1- is bonded in a distorted bent 150 degrees geometry to two Al3+ atoms. In the second F1- site, F1- is bonded in a distorted single-bond geometry to two Al3+ atoms. In the third F1- site, F1- is bonded in a linear geometry to two equivalent Al3+ atoms. In the fourth F1- site, F1- is bonded in a bent 150 degrees geometry to two equivalent Al3+ atoms. In the fifth F1- site, F1- is bonded in a water-like geometry to two Al3+ atoms. In the sixth F1- site, F1- is bonded in a water-like geometry to two Al3+ atoms.
AlF3 is alpha Rhenium trioxide structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Al3+ is bonded to six equivalent F1- atoms to form corner-sharing AlF6 octahedra. The corner-sharing octahedral tilt angles are 0°. All Al–F bond lengths are 1.82 Å. F1- is bonded in a linear geometry to two equivalent Al3+ atoms.
Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations
The development of optical systems operating in the far ultraviolet range (FUV, λ=100-200 nm) is limited by the efficiency of passivated aluminum (Al) mirrors. Although it is presently possible to obtain high-reflectivity FUV mirrors through physical vapor deposition, the process involves deposition with substrates at high temperatures, which is technically challenging for large optical elements. A novel passivation procedure for bare Al mirrors is reported. The treatment consisted of using a low-temperature electron-beam generated plasma produced in a gas mixture of Ar and SF6 to etch away the native oxide layer from the Al film, while simultaneously promoting the generation of a thin aluminum tri-fluoride (AlF3) layer on the Al surface. In the first section we analyze the effect of varying both ion energy and SF6 concentration on the FUV reflectance, thickness, composition, and surface morphology of the resulting AlF3 protective layers. In the second section, the reflectivity of samples is optimized at selected important FUV wavelengths for astronomical observations. Notably, samples attained state-of-the-art reflectances of 75% at 108.5 nm (He Lyman γ), 91% at 121.6 nm (H Lyman α), 90% at 130.4 nm (OI), and of 95% at 155.0 nm (C IV). The stability over time of these passivated mirrors is also investigated.
Understanding molten salt chemistry is essential in ongoing research of the molten salt nuclear reactor (MSR). In this context, detailed understanding of the mechanisms underlying selective oxidation of metal species, such as Cr, is required to guide the design of effective corrosion mitigation strategies in molten salts. An important starting point for such mechanistic understanding is knowledge of the solvation structure and its role in controlling metal speciation. In this work, we use ab initio molecular dynamics simulations to study the short-range (on the scale of the nearest-neighbor bond lengths) and medium-range (over length scales of several neighbor spacings) structure in three different fluoride melts with and without Cr addition; namely, 2KF-NaF, 2LiF-BeF 2 , and 3LiF-AlF3. We find that Cr 0 ,Cr 2+ ,Cr 3+ can each be coordinated by different numbers of F-, with the variance in coordination number decreasing as oxidation state increases, and that these coordination geometries are largely independent of solvent. The manner by which Cr changes the medium-range structure, however, is found to be solvent-dependent. While 2KF-NaF melts show short and medium range order that is highly dynamic, 2LiF-BeF 2 and 3LiF-AlF 3 are characterized by molecular associates that are relatively long-lived that organize into oligomer structures on larger length scales. Rather than being solvated by F- ions alone, we find that Cr can incorporate into and be solvated within this oligomer structure. Fluoroacidity, alone, may therefore prove too simple a metric for assessing the corrosivity of molten fluorides. As our work suggests, the ability of Cr to solvate must be understood in the context of the short- and medium-range structure of the solvent.
While lithium, manganese-rich (LMR) layered oxide cathode materials offer high energy density (>900 Wh kg –1 ) and low cost, LMR is susceptible to continuous capacity and voltage decay from the oxygen migration and side reaction with aqueous electrolyte at high voltage. Herein, the integration of Na/F co-doping (CD) and AlF 3 coating on LMR is achieved without the need of complex atomic layer deposition. Akin to pristine and CD samples, CD with 1 wt % AlF 3 (CD-1.0 wt %) shows excellent electrochemical performance with the capacity and voltage retentions of 93 and 91% after 150 cycles at 0.5C, respectively, and increased ionic conductivity. Spectroscopic analysis indicates that the coating mainly influences the Co distribution, where Co is enriched on the surface, and partial diffusion of Al 3+ ions toward the bulk, leading to a slight change of transition-metal (TM) valence states at the nanometer scale and the formation of a stable Li x (CoAl)O y phase. Post-cycling analysis reveals that CD-1.0 wt % can alleviate the formation of rock-salt structure and Mn dissolution. Besides, little to no metal segregation is detected for the cycled CD-1.0 wt % sample. This finding presents the first instance to apply co-doping and AlF 3 coating as a new strategy to enhance the structural homogeneity and takes another step toward their commercial viability.