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The structure of MgO-SiO2 glasses at elevated pressure.
MedLine Citation:
PMID:  22580970     Owner:  NLM     Status:  PubMed-not-MEDLINE    
Abstract/OtherAbstract:
The magnesium silicate system is an important geophysical analogue and neutron diffraction data from glasses formed in this system may also provide an initial framework for understanding the structure-dependent properties of related liquids that are important during planetary formation. Neutron diffraction data collected in situ for a single composition (38 mol% SiO(2)) magnesium silicate glass sample shows local changes in structure as pressure is increased from ambient conditions to 8.6 GPa at ambient temperature. A method for obtaining the fully corrected, total structure factor, S(Q), has been developed that allows accurate structural characterization as this weakly scattering glass sample is compressed. The measured S(Q) data indicate changes in chemical ordering with pressure and the real-space transforms show an increase in Mg-O coordination number and a distortion of the local environment around magnesium ions. We have used reverse Monte Carlo methods to compare the high pressure and ambient pressure structures and also compare the high pressure form with a more silica-poor glass (Mg(2)SiO(4)) that represents the approach to a more dense, void-free and topologically ordered structure. The Mg-O coordination number increases with pressure and we also find that the degree of continuous connectivity of Si-O bonds increases via a collapse of interstices.
Authors:
Martin Wilding; Malcolm Guthrie; Shinji Kohara; Craig L Bull; Jaakko Akola; Matt G Tucker
Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.     Date:  2012-05-11
Journal Detail:
Title:  Journal of physics. Condensed matter : an Institute of Physics journal     Volume:  24     ISSN:  1361-648X     ISO Abbreviation:  J Phys Condens Matter     Publication Date:  2012 Jun 
Date Detail:
Created Date:  2012-05-17     Completed Date:  2012-09-12     Revised Date:  2012-09-25    
Medline Journal Info:
Nlm Unique ID:  101165248     Medline TA:  J Phys Condens Matter     Country:  England    
Other Details:
Languages:  eng     Pagination:  225403     Citation Subset:  -    
Affiliation:
Institute of Mathematical and Physical Sciences, Aberystwyth University, Aberystwyth, UK. mbw@aber.ac.uk
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Erratum In:
J Phys Condens Matter. 2012 Aug 22;24(33):339501

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