Japan Geoscience Union Meeting 2014

Presentation information

Oral

Symbol S (Solid Earth Sciences) » S-MP Mineralogy & Petrology

[S-MP47_1AM2] Physics and Chemistry of Minerals

Thu. May 1, 2014 11:00 AM - 12:45 PM 422 (4F)

Convener:*Hiroki Okudera(School of Natural System, College of Science and Engineering), Atsushi Kyono(Graduate School of Life and Environmental Sciences, University of Tsukuba), Chair:Takuo Okuchi(Institute for Study of the Earth's Interior, Okatama University), Hiroaki Ohfuji(Geodynamics Research Center, Ehime University)

12:00 PM - 12:15 PM

[SMP47-12] Structure refinement of legrandite and paradamite : crystal chemistry and hydrogen bonds

*Satoshi JINNOUCHI1, Akira YOSHIASA1, Kazumasa SUGIYAMA2, Hiroshi ARIMA2, Reiko SHIMURA2, Riturou MIYAWAKI3 (1.Graduate School of Science and Technology, Kumamoto University., 2.Institute for Materials Research, Tohoku University, 3.National Science Museum)

Keywords:structure refinement, legrandite, paradamite, crystal chemistry, hydrogen bonds

Legrandite, Zn2AsO4(OH)H2O and paradamite, Zn2AsO4(OH), are zinc arsenate minerals and have a color between pale yellow and yellowish brown. Related minerals of legrandite and paradamite are adamite, Zn2AsO4(OH), and so on with different structures. We performed the structure refinement of legrandite and paradamite Oujela Mine, Mapimi, Durango, Mexico, by (RAPID) RIGAKU single-crystal structure analysis system. We determined the hydrogen position by difference Fourier method. We revealed the detail hydrogen bond using bond valence calculation and hydrogen positions and compared crystal structures of these. The structure of legrandite is constituted by two AsO4 tetrahedrons, ZnO6 octahedron and three ZnO5 trigonal dipyramids that have large unique distortion. AsO4 tetrahedron, ZnO5 trigonal dipyramid and ZnO6 octahedron constitutes the unique framework. The structure of paradamite is constituted by AsO4 tetrahedron and two ZnO5 trigonal dipyramid that have large unique distortion. In legrandite, 5 coordination of trigonal dipyrmids have a distance to be expected from ionic radii but interatomic distance of Zn(3)-O(1) has extraordinary distance. Two OH groups bond to Zn1 and Zn2, Zn3 and Zn4 make the ZnO3(H2O)2 trigonal dipyramid that is bonded to two H2O group in legrandite. In paradamite, Zn1 and Zn2 make ZnO3(OH)2 and ZnO4(OH) trigonal dipyramid. Hydrogen atoms make a lot of hydrogen bonding in legrandite and paradamite. Crystal structure of legrandite has a tunnel structure continuous that is only parallel to c axis and similar structure is observed in paradamite only parallel to a axis. There are path of proton-conduction in these direction and we conjecture that these proton-conductivity have large anisotropy of one dimension.