silver surface energy wulff construction wolfram player

Outside the f-block, the β-YF 3-structure is experimentally known for bismuth trifluoride and predicted as an accessible meta-stable phase for the trichlorides of Y(III) and Bi(III). Interestingly, the known orthorhombic low-temperature phase of plutonium trihydride is also reasoned to be an exotic example of a β-YF 3 structure. Due to the often observed analogy of actinides to lanthanides, the same crystal structure is assumed for the, so far, experimentally unknown heavier actinide trifluorides of Es(III)–Lr(III). The same low-temperature phase is also found for the two actinides Bk(III) and Cf(III). Consequently, all their trifluorides crystallize as well in β-YF 3. The ionic radii of the middle and late lanthanides Sm(III)–Lu(III) differ by only ≤6 pm compared to Y(III). This is their only stable phase up to 1343 K (HoF 3) or 1350 K (YF 3), which is well beyond the temperature regime of hydrothermal fluids of typically 323–873 K. In accordance with their twin behavior, solid YF 3 and HoF 3 occur in the same crystal structure type of β-YF 3 (space group Pnma, fully occupied Wyckoff positions (Y) 4c, (F) 4c, (F) 8d ( Figure 1)). To lay one foundation for future quantum chemical studies on the different fluorine-affinity of yttrium and holmium, we started with an investigation of the respective trifluorides and their surfaces. It is suggested that one underlying reason for the twin separation is their different affinity to fluorine, which was found in dissolving experiments of YF 3 and HoF 3 in diluted hydrofluoric acid. Interestingly, those fluoride-rich hydrothermal fluids produce ores with a non-chondritic excess of yttrium over holmium. Fluoride plays a significant role in accumulating HFSE and REE within hydrothermal fluids, as these cations do not form such stable complexes with chloride. In nature, YF 3 is found within the mineral waimirite-(Y), which contains high concentrations of other REE. Moreover, YF 3 and HoF 3 are important precursors for the synthesis of the respective pure metallic compounds. HoF 3 is interesting for magnetic high-field applications as, e.g., a contrast agent, due to the very high magnetic moment of holmium. Another emerging field of application is solid-state fluoride batteries, resulting from the very high conductivity of fluoride anions. Doped with trivalent REE cations, YF 3 is also applicable as an optical filter in 157-nm photolithography. The wide-band-gap material YF 3 has very good properties for laser applications. Īs fluorides, both metals can be used for different specific applications. Due to their twin character, yttrium is also often associated with that group. As a lanthanide, holmium also belongs to the rare earth elements (REE). According to their small ionic radii of 1.075 Å (Y) and 1.072 Å (Ho) in nine-fold coordination and their high oxidation state, both belong to the interesting group of high field strength elements (HFSE). The term emphasizes their identical geochemical behavior caused by the equal ratio of charge to radius in their only stable oxidation state +III. Yttrium and holmium form a geochemical twin pair. However, subtle differences have been found between these two geochemical twins. The stoichiometric (010) surface is dominating in both compounds. The resulting Wulff plots consists of seven surfaces with 5–26% abundance for YF 3 and six surfaces with 6–34% for HoF 3. This leads to a scope of 24 terminations per compound. All seven low-lying Miller indices surfaces are considered with all possible stoichiometric or substoichiometric terminations with a maximal fluorine-deficit of two. An extensive surface stability analysis of YF 3 (PBE) and HoF 3 (PBE+U d/3 eV/4f-in-core) using two-dimensional surface models (slabs) is performed. Interestingly, it has been found that DFT/DFT+U describe bulk HoF 3 best, when the 4f-electrons are excluded from the valence region. Due to their equivalent geochemical behavior, both elements form a geochemical twin pair and consequently, yttrium is generally associated with the REE as REE+Y. As a lanthanide, holmium also belongs to the group of rare earth elements (REE). The trifluorides of the two high field strength elements yttrium and holmium are studied by periodic density functional theory.

Silver surface energy wulff construction wolfram player