@article{49ef3bba9a8c4a44a31fbc5c4aeddc6e,
title = "A new high-pressure phase transition in natural gedrite",
abstract = "High-pressure diamond-anvil cell synchrotron X-ray diffraction experiments were conducted on single-crystal samples of natural orthoamphibole; gedrite; with composition; (K0.002Na0.394)(Mg2)(Mg1.637Fe2.245Mn0.004Ca0.022Cr0.003Na0.037Al1.052)(Si6.517Al1.483)O22(OH)2. The samples were compressed at 298 K up to a maximum pressure of 27(1) GPa. In this pressure regime, we observed a displacive phase transition between 15.1(7) and 21(1) GPa from the orthorhombic Pnma phase to a new structure with space group P21/m; which is different from the familiar P21/m structure of cummingtonite and retains the (+, +, −, −) I-beam stacking sequence of the orthorhombic structure. The unit cell parameters for the new phase at 21(1) GPa are a = 17.514(3), b = 17.077(1), c = 4.9907(2) {\AA} and β = 92.882(6)◦. The high-pressure P21/m phase is the first amphibole structure to show the existence of four crystallographically distinct silicate double chains. The orthorhombic to monoclinic phase transition is characterized by an increase in the degree of kinking of the double silicate chains and is analogous to displacive phase changes recently reported in orthopyroxenes, highlighting the parallel structural relations and phase transformation behavior of orthorhombic single-and double-chain silicates.",
keywords = "Amphibole, Diamond anvil cell, High-pressure, Phase transition, Single-crystal X-ray diffraction, Synchrotron source",
author = "Tommy Yong and Bina, {Craig R.} and Finkelstein, {Gregory J.} and Dongzhou Zhang and Przemyslaw Dera",
note = "Funding Information: The project was supported by the National Science Foundation grant EAR 1722969. Portions of the X-ray diffraction work were conducted using the X-ray Atlas instrument at the University of Hawaii, funded by NSF grant EAR 1541516. Portions of this work were performed at GeoSoilEnviroCARS (Sector 13), Advanced Photon Source (APS), and Argonne National Laboratory. PX?2 program and the COMPRES-GSECARS gas loading system are supported by COMPRES under NSF Cooperative Agreement EAR-1661511. GeoSoilEnviroCARS is supported by the National Science Foundation?Earth Sciences (EAR-1128799) and Department of Energy?Geosciences (DE-FG02-94ER14466). Use of the Advanced Photon Source was supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. Funding Information: Funding: The project was supported by the National Science Foundation grant EAR 1722969. Portions of the X-ray diffraction work were conducted using the X-ray Atlas instrument at the University of Hawaii, funded by NSF grant EAR 1541516. Portions of this work were performed at GeoSoilEnviroCARS (Sector 13), Advanced Photon Source (APS), and Argonne National Laboratory. PXˆ2 program and the COMPRES-GSECARS gas loading system are supported by COMPRES under NSF Cooperative Agreement EAR-1661511. GeoSoilEnviroCARS is supported by the National Science Foundation—Earth Sciences (EAR-1128799) and Department of Energy—Geosciences (DE-FG02-94ER14466). Use of the Advanced Photon Source was supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. Publisher Copyright: {\textcopyright} 2019 by the authors. Licensee MDPI, Basel, Switzerland.",
year = "2019",
month = oct,
doi = "10.3390/cryst9100521",
language = "English (US)",
volume = "9",
journal = "Crystals",
issn = "2073-4352",
publisher = "Multidisciplinary Digital Publishing Institute (MDPI)",
number = "10",
}