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Analyzing Melts and Fluids from Ab Initio Molecular Dynamics Simulations with the UMD Package
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Structure and dynamics of high-temperature strontium aluminosilicate melts
Pierre Florian1, Alexey Novikov, James W E Drewitt
1CNRS, CEMHTI UPR3079, Université d'Orléans, F-45071 Orléans, France. pierre.florian@cnrs-orleans.fr.
Physical Chemistry Chemical Physics : PCCP
|November 7, 2018
Summary
This study explores high-temperature SrO-Al2O3-SiO2 melts and glasses. Aluminum-silicate structures and dynamics were investigated using advanced techniques, revealing key insights into melt behavior and coordination.
Area of Science:
- Materials Science
- Geochemistry
- Solid State Chemistry
Background:
- Understanding the structure and dynamics of high-temperature oxide melts is crucial for materials processing and geological applications.
- The SrO-Al2O3-SiO2 system represents a complex multi-component oxide relevant to various industrial and natural processes.
- Previous studies have explored phase equilibria but lacked detailed structural and dynamic information at extreme temperatures.
Purpose of the Study:
- To investigate the structural evolution and dynamics of SrO-Al2O3-SiO2 melts and glasses across a range of compositions and temperatures (1600-2300 °C).
- To correlate melt structure, coordination environments of Al and Sr, and dynamic properties like viscosity and diffusion.
- To elucidate the role of aluminum coordination and its dependence on melt composition and temperature.
Main Methods:
- High-temperature 27Al Nuclear Magnetic Resonance (NMR) spectroscopy to probe aluminum environments and dynamics.
- High-temperature neutron diffraction to determine atomic-scale structure and coordination.
- Measurement of macroscopic shear viscosity and analysis of NMR relaxation times for dynamic correlations.
Main Results:
- Polymerized melts exhibit a random distribution of Al and Si in tetrahedral sites, while depolymerized melts form smaller rings.
- Five-fold coordinated aluminum (VAl) sites are present in most compositions, with high amounts in per-aluminous glasses/melts.
- Strontium coordination number decreases from glass to melt, and melt dynamics correlate well between NMR relaxation and viscosity.
Conclusions:
- The aluminum environment's temperature dependence is primarily governed by the distribution of Al-(OSi)p(OAl)(4-p) units.
- Oxygen self-diffusion decreases with increasing Si/(Al + Si) ratio in polymerized melts.
- Structural and dynamic properties of these complex oxide melts are highly sensitive to compositional variations.
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