The structure of MgO-SiO2 glasses at elevated pressure

Martin Charles Wilding, Malcolm Guthrie, Shinji Kohara, Craig L. Bull, Jaakko Akola, Matt G. Tucker

Allbwn ymchwil: Cyfraniad at gyfnodolynErthygladolygiad gan gymheiriaid

18 Dyfyniadau(SciVal)

Crynodeb

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% SiO2) 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 (Mg2SiO4) 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.

Iaith wreiddiolSaesneg
Rhif yr erthygl225403
Nifer y tudalennau11
CyfnodolynJournal of Physics: Condensed Matter
Cyfrol24
Rhif cyhoeddi22
Dynodwyr Gwrthrych Digidol (DOIs)
StatwsCyhoeddwyd - 06 Meh 2012

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