An in situ Raman spectroscopic study of Na 2 Si 2 O 5 at high pressures and temperatures; structures of compressed liquids and glasses

Other| April 01, 1996 An in situ Raman spectroscopic study of Na 2 Si 2 O 5 at high pressures and temperatures; structures of compressed liquids and glasses Daniel L. Farber; Daniel L. Farber University of California at Santa Cruz, Department of Earth Sciences and Institute of Tectonics, Santa Cruz, CA, United States Search for other works by this author on: GSW Google Scholar Quentin Williams Quentin Williams Search for other works by this author on: GSW Google Scholar Author and Article Information Daniel L. Farber University of California at Santa Cruz, Department of Earth Sciences and Institute of Tectonics, Santa Cruz, CA, United States Quentin Williams Publisher: Mineralogical Society of America First Online: 02 Mar 2017 Online Issn: 1945-3027 Print Issn: 0003-004X Copyright © 1996 by the Mineralogical Society of America American Mineralogist (1996) 81 (3-4): 273–283. https://doi.org/10.2138/am-1996-3-402 Article history First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Daniel L. Farber, Quentin Williams; An in situ Raman spectroscopic study of Na 2 Si 2 O 5 at high pressures and temperatures; structures of compressed liquids and glasses. American Mineralogist 1996;; 81 (3-4): 273–283. doi: https://doi.org/10.2138/am-1996-3-402 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyAmerican Mineralogist Search Advanced Search Abstract Raman spectra of Na2Si2O5 glass and Na2Si2O5 liquid have been collected in situ to pressures of 16 GPa at 300 K and 10 GPa at 885 K. In glass compressed at 300 K, bands associated with intertetrahedral bridging O atoms decrease in intensity and ultimately become unresolvable above 8 GPa. Over this same pressure range, new peaks appear in the glass between 600 and 800 cm–1; these new features are consistent with the formation of SiO5 or SiO6 polyhedra through the destruction of nonbridging O atoms. Between ~10 and 16 GPa, band intensities shift, the total integrated Raman scattering intensity of the glass decreases by more than a factor of ten, and the pressure dependence of mode shifts changes. These changes are consistent with a new densification mechanism initiated in the glass above ~8 GPa, probably from the formation of linkages between two or more highly coordinated Si atoms. No vibrations attributed to bridged silica tetrahedra are observed in the liquid above 8 GPa, indicating that at least 50% of the Si in the liquid at 8 GPa is highly coordinated. Upon decompression of thermally quenched samples at 300 K, bands associated with bridged tetrahedra reappear at pressures below 1 GPa. Similarly, glasses that have been compressed only at 300 K and then decompressed have bands associated with bridged tetrahedra. The formation of bands associated with bridged tetrahedra on decompression both in glasses quenched from liquids formed at high-pressure and in glasses compressed at 300 K demonstrates that these species arise from structural reorganizations during decompression. Such reorganizations plausibly involve the breakdown of highly coordinated Si polyhedra and the resultant formation of bridged tetrahedra. The nearly complete decomposition of the high-pressure structure in glasses on decompression documents that in situ high-pressure measurements are crucial in deriving accurate constraints on the structure of silicate liquids at high pressure. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.