Incommensurately modulated structure of Zn4Si2O7(OH)2·H2O at high pressure
Roman Gajda,
Wojciech Sławiński,
Tomasz Poręba,
Jan Parafiniuk,
Mohamed Mezouar,
Przemysław Dera,
Krzysztof Woźniak
Affiliations
Roman Gajda
Faculty of Chemistry, University of Warsaw, Pasteura 1, Warszawa, 02-089, Poland
Wojciech Sławiński
Faculty of Chemistry, University of Warsaw, Pasteura 1, Warszawa, 02-089, Poland
Tomasz Poręba
European Synchrotron Radiation Facility, 71 Avenue des Martyrs, Grenoble, 38000, France
Jan Parafiniuk
Institute of Geochemistry, Mineralogy and Petrology, Department of Geology, University of Warsaw, Żwirki i Wigury 101, Warszawa, 02-089, Poland
Mohamed Mezouar
European Synchrotron Radiation Facility, 71 Avenue des Martyrs, Grenoble, 38000, France
Przemysław Dera
Hawaii Institute of Geophysics and Planetology, School of Ocean and Earth Science and Technology, University of Hawaii at Manoa, 1680 East West Road, POST Bldg, Office 819E, Honolulu, Hawaii 96822, USA
Krzysztof Woźniak
Department of Chemistry, Biological and Chemical Research Centre, University of Warsaw, Żwirki i Wigury 101, Warszawa, 02-089, Poland
High-resolution single-crystal X-ray diffraction experiments on Zn4Si2O7(OH)2·H2O hemimorphite were conducted at high pressure using diamond anvil cells at several different synchrotron facilities (ESRF, Elettra, DESY). Experimental data confirmed the existence of a previously reported phase transition and revealed the exact nature of the incommensurate modulation. We report the incommensurately modulated structure described in the (3+1)D space group Pnn2(0, β, 0)000. We have determined the modulation mechanism, which involves the fluctuation of atoms between two main positions, occurring mainly along the [100] direction, perpendicular to the modulation vector. Moreover, our results reveal that the phase transition occurs at lower pressure than previously reported.
