title: Crystal structure of magnesium dichloride decahydrate determined by X-ray and neutron diffraction under high pressure.
abstract: Magnesium dichloride decahydrate (MgCl2·10H2O) and its deuterated counterpart (MgCl2·10D2O) are identified for the first time by in-situ powder synchrotron X-ray and spallation neutron diffraction. These substances are crystallized from a previously unidentified nanocrystalline compound, which originates from an amorphous state at low temperature. A combination of a recently developed autoindexing procedure and the charge-flipping method reveals that the crystal structure of MgCl2·10H2O consists of an ABCABC··· sequence of Mg(H2O)6 octahedra. The Cl(-) anions and remaining water molecules unconnected to the Mg(2+) cations bind the octahedra, similar to other water-rich magnesium dichloride hydrates. The D positions in MgCl2·10D2O, determined by the difference Fourier methods using the neutron powder diffraction patterns at 2.5 GPa, show the features such as bifurcated hydrogen bonds and tetrahedrally coordinated O atoms, which were not found in other forms of magnesium chloride hydrates.
authors: Geochemical Research Center, Graduate School of Science, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan.
authors: Kazuki
authors: K
authors: Komatsu
authors: Geochemical Research Center, Graduate School of Science, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan.
authors: Ayako
authors: A
authors: Shinozaki
authors: Comprehensive Research Organization for Science and Society, IQBRC Bldg, 162-1 Shirakata, Tokai, Naka, Ibaraki 319-1106, Japan.
authors: Shinichi
authors: S
authors: Machida
authors: Geochemical Research Center, Graduate School of Science, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan.
authors: Takuto
authors: T
authors: Matsubayashi
authors: Geochemical Research Center, Graduate School of Science, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan.
authors: Mao
authors: M
authors: Watanabe
authors: Geochemical Research Center, Graduate School of Science, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan.
authors: Hiroyuki
authors: H
authors: Kagi
authors: Quantum Beam Science Directorate, Japan Atomic Energy Agency, 2-4 Shirakata-Shirane, Tokai-mura, Ibaraki 319-1195, Japan.
authors: Asami
authors: A
authors: Sano-Furukawa
authors: Quantum Beam Science Directorate, Japan Atomic Energy Agency, 2-4 Shirakata-Shirane, Tokai-mura, Ibaraki 319-1195, Japan.
authors: Takanori
authors: T
authors: Hattori
keywords: X-ray powder diffraction; charge-flipping method; high pressure; magnesium dichloride hydrate; spallation neutron diffraction