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American Mineralogist

Journal of Earth and Planetary Materials

Ed. by Baker, Don / Xu, Hongwu

IMPACT FACTOR 2018: 2.631

CiteScore 2018: 2.55

SCImago Journal Rank (SJR) 2018: 1.355
Source Normalized Impact per Paper (SNIP) 2018: 1.103

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Volume 97, Issue 11-12


First-principles study of self-diffusion and viscous flow in diopside (CaMgSi2O6) liquid

Ashok K. Verma
  • High Pressure and Synchrotron Radiation Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, India
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/ Bijaya B. Karki
  • Department of Computer Science, Department of Geology and Geophysics, Center of Computation and Technology, Louisiana State University, Baton Rouge, Louisiana 70803, U.S.A.
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Published Online: 2015-04-02 | DOI: https://doi.org/10.2138/am.2012.4123


We have carried out equilibrium molecular dynamics simulations of CaMgSi2O6 (diopside) liquid as a function of pressure (up to 150 GPa) and temperature (2200 to 6000 K) using density functional theory. Self-diffusion of Mg/Ca atoms decouples most from that of framework (Si/O) atoms at 2200 K and zero pressure, and all diffusivities become increasingly similar as temperature and pressure increase. The predicted temperature variations of all transport coefficients at zero pressure closely follow the Arrhenian law with activation energies of 107 to 161 kJ/mol. However, their pressure variations show significant deviations from the Arrhenius behavior. Along the 3000 K isotherm, the Si and O self-diffusivities show non-monotonic variations up to 20 GPa and then rapidly decrease upon further compression. The melt viscosity also shows a weak anomaly in the low-pressure regime before it starts to increase rapidly with pressure. Our results agree favorably with experimental observations of low-pressure non-uniform variations of Si and O self-diffusivities and viscosity. The predicted complex dynamical behavior requires pressure-volume dependent activation volumes and can be associated with structural changes occurring on compression.

Keywords : Diopside liquid; diffusion; viscosity; first-principles simulations; high pressure

About the article

Received: 2012-02-04

Accepted: 2012-07-26

Published Online: 2015-04-02

Published in Print: 2012-11-01

Citation Information: American Mineralogist, Volume 97, Issue 11-12, Pages 2049–2055, ISSN (Online) 1945-3027, ISSN (Print) 0003-004X, DOI: https://doi.org/10.2138/am.2012.4123.

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