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 a...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.展开更多
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 LaboratoryThe PX2 program is supported by COMPRES under NSF Cooperative Agreement No.EAR 11-57758+3 种基金The use of the COMPRES-GSECARS gas loading system was supported by COMPRES under NSF Cooperative Agreement No.EAR 11-57758 and by GSECARSGeoSoilEnviroCARS 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.
文摘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.
