The distribution of Ga and A1 atoms within the octahedral sheets of synthetic goethites has been investigated by XRD and Ga K-edge XANES and EXAFS spectroscopies. XRD results indic te a solid solution between goethite (aFeOOH) and GaGoe4 (40 mol% of Ga). The XANES data indicate the presence of &a in the solid solution. The fitting procedures for EXAFS spectra show no evidence of preferential oc...

The crystal structures of the [A(1)(2)][A(2)(3)](BO(4))(3)X apatites and the related compounds [A(1)(2)][A(2)(3)](BO(5))(3)X and [A(1)(2)][A(2)(3)](BO(3))(3)X are collated and reviewed. The structural aristotype for this family is Mn(5)Si(3) (D8(8) type, P6(3)/mcm symmetry), whose cation array approximates that of all derivatives and from which related structures arise through the systematic in...

Four thorium sulfate compounds have been synthesized and characterized. [Th(SO4)2(H2O)7] 2H2O (ThS1) crystallizes in space group P21/m, a1⁄47.2488(4), b1⁄412.1798(7), c1⁄48.0625(5) Å, b1⁄498.245(1); Na10[Th2(SO4)9(H2O)2] 3H2O (ThS2), Pna21, a1⁄417.842(2), b1⁄46.9317(8), c1⁄427.550(3) Å; Na2[Th2(SO4)5 (H2O)3] H2O (ThS3), C2/c, a1⁄416.639(2), b1⁄49.081(1), c1⁄425.078(3) Å, b1⁄4 95.322(2); [Th4(SO...

Samples of dark to black fayalite from ten localities around the world were examined by 57Fe Mossbauer spectroscopy to see if any contained significant proportions of ferric iron. Of these ten samples, four, including a sample of ferrifayalite from Qianan County, China, previously known to contain ferric iron, were found to contain large amounts of this cation. Ferric/ferrous ratios of these sa...

Hydrogen incorporation in aluminous orthopyroxene may control the generation of melt and dominate the seismic properties at the base of the Earth’s lithosphere. To clarify the substitution mechanism of H, we have synthesized, characterized, and refi ned the crystal structure of this potentially signifi cant variant of orthopyroxene. The experimentally produced crystals are small needles up to a...

Oxygen is the most abundant element in the Earth, constituting about 43 percent by weight of the crust and mantle. While most of this mass is incorporated into silicates, the next most abundant mineral group in the planet is the oxides. The oxide minerals are generally considered to be those oxygen-based minerals that do not contain a distinct polyanionic species such as OH, CO3, SO4 PO4, SiO4,...

VIII VI IV Aenigmatite, Na4 (Fe2 +,Ti,Fe 3 +) 1 2 (SiFe 3 +) 12 0 40 , is a common constituent of sodium-rich alkaline igneous rocks and is classified as an open-branched single-chain silicate, whose structure is closely related to that of sapphirine. The first Mossbauer spectra of three valid aenigmatite specimens were recorded and the detailed crystal chemistry were obtained. In the Mossbauer...

Liquid crystals have a major impact on our modern society, reaching from simple digital calculators to high-resolution flat-panel displays, and their market volume is expected to further increase. For example, in 2010 revenues of €1,013 million from sales of liquid crystals were reported by Merck, the world’s largest supplier of liquid crystal materials for electro-optical applications. This in...

Carbon allotropes have been explored intensively by ab initio crystal structure prediction, but such methods are limited by the large computational cost of the underlying density functional theory (DFT). Here we show that a novel class of machine-learning-based interatomic potentials can be used for random structure searching and readily predicts several hitherto unknown carbon allotropes. Rema...

Through the complementary use of single-crystal X-ray diffraction and X-ray absorption spectroscopy, we present in this paper the first direct results on the site occupancy of thorium in the fluorapatite structure and the structural distortion created by its substitution. Structure refinements based on single-crystal X-ray diffraction data from synthetic Th-doped fluorapatite indicates that Th ...