Partnership for eXtreme Xtallography (PX^(2))—A state-of-the-art experimental facility for extreme-conditions crystallography: A case study of pressure-induced phase transition in natural ilvaite  

作　　者：Jingui Xu Dongzhou Zhang Sergey N.Tkachev Przemyslaw K.Dera 

机构地区：[1]School of Ocean and Earth Science and Technology,Hawai’i Institute of Geophysics and Planetology,University of Hawai’i at Manoa,Honolulu,Hawaii 96822,USA [2]Center for Advanced Radiation Sources,University of Chicago,Chicago,Illinois 60437,USA

出　　处：《Matter and Radiation at Extremes》2022年第2期62-71,共10页极端条件下的物质与辐射（英文）

基　　金：This work was performed at GeoSoilEnviroCARS(The University of Chicago,Sector 13),Partnership for Extreme Crystallography(PX2)program,Advanced Photon Source(APS),and Argonne National Laboratory;The PX2 program is supported by COMPRES under NSF Cooperative Agreement No.EAR 11-57758;The use of the COMPRES-GSECARS gas loading system was supported by COMPRES under NSF Cooperative Agreement No.EAR 11-57758 and by GSECARS;GeoSoilEnviroCARS is supported by the National Science Foundation-Earth Sciences(Grant No.EAR-1634415);Department of Energy-GeoSciences(Grant No.DE-FG02-94ER14466);This research used resources of the Advanced Photon Source,a U.S.Department of Energy(DOE)Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No.DE-AC02-06CH11357.

摘　　要：Single-crystal x-ray diffraction(SCXRD)is an important tool to study the crystal structure and phase transitions of crystalline materials at elevated pressures.The Partnership for eXtreme Xtallography(PX^(2))program at the GSECARS 13-BM-C beamline of the Advanced Photon Source aims to provide state-of-the-art experimental capabilities to determine the crystal structures of materials under extreme conditions using SCXRD.PX^(2) provides a focused x-ray beam(12318μm^(2))at a monochromatic energy of 28.6 keV.High-pressure SCXRD experiments are performed with a six-circle diffractometer and a Pilatus3 photon-counting detector,facilitated by a membrane system for remote pressure control and an online ruby fluorescence system for pressure determination.The efficient,high-quality crystal structure determination at PX^(2) is exemplified by a study of pressure-induced phase transitions in natural ilvaite[CaFe^(2+)_(2 )Fe^(3+)Si_(2)O_(7)O(OH),P2_(1)/a space group].Two phase transitions are observed at high pressure.The SCXRD data confirm the already-known ilvaite-I(P2_(1)/a)→ilvaite-II(Pnam)transformation at 0.4(1)GPa,and,a further phase transition is found to occur at 22.8(2)GPa where ilvaite-II transforms into ilvaite-III(P2_(1)/a).The crystal structure of the ilvaite-III is solved and refined in the P2_(1)/a space group.In addition to the ilvaite-I→ilvaite-II→ilvaite-III phase transitions,two minor structural modifications are observed as discontinuities in the evolution of the FeO6 polyhedral geometries with pressure,which are likely associated with magnetic transitions.

关 键 词：phase EXTREME transitions 

分 类 号：O434.1[机械工程—光学工程]