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First-principles study of self-diffusion and viscous flow in diopside (CaMgSi2O6) liquid
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Ashok K. Verma
Published/Copyright:
April 2, 2015
Abstract
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.
Received: 2012-2-4
Accepted: 2012-7-26
Published Online: 2015-4-2
Published in Print: 2012-11-1
© 2015 by Walter de Gruyter Berlin/Boston
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Keywords for this article
Diopside liquid;
diffusion;
viscosity;
first-principles simulations;
high pressure
Articles in the same Issue
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- Blue spinel crystals in the MgAl2O4-CoAl2O4 series: Part I. Flux growth and chemical characterization
- Blue spinel crystals in the MgAl2O4-CoAl2O4 series: Part II. Cation ordering over short-range and long-range scales
- CO2 solubility in primitive martian basalts similar to Yamato 980459, the effect of composition on CO2 solubility of basalts, and the evolution of the martian atmosphere
- New structural features of the high-pressure synthetic sheet-disilicate Phase-X, K(2–x)Mg2Si2O7Hx
- Crystal structure refinements of borate dimorphs inderite and kurnakovite using 11B and 25Mg nuclear magnetic resonance and DFT calculations
- Hydrogen-bond system and dehydration behavior of the natural zeolite parthéite
- In situ dehydration behavior of zeolite-like cavansite: A single-crystal X-ray study
- LREE-redistribution among fluorapatite, monazite, and allanite at high pressures and temperatures
- A single-crystal neutron diffraction study of hambergite, Be2BO3(OH,F)
- Analyzing water contents in unexposed glass inclusions in quartz crystals
- The atomic structure of deuterated boyleite ZnSO4·4D2O, ilesite MnSO4·4D2O, and bianchite ZnSO4·6D2O
- Synthesis and crystal chemistry of Fe3+-bearing (Mg,Fe3+)(Si,Fe3+)O3 perovskite
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- Structural regularities in 2M1 dioctahedral micas: The structure modeling approach
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- Browneite, MnS, a new sphalerite-group mineral from the Zakłodzie meteorite
- Mineralogical variation of silica induced by Al and Na in hydrothermal solutions
