Atomistic characterization of the SiO2 high-density liquid/low-density liquid interface.
Xin Zhang1, Brian B Laird2, Hongtao Liang1
1State Key Laboratory of Precision Spectroscopy, School of Physics and Electronic Science, East China Normal University, Shanghai 200241, China.
The Journal of Chemical Physics
|October 8, 2022
Summary
Molecular-dynamics simulations reveal a spatial fragile-to-strong transition at the silica liquid-liquid interface. This interface shows unique mixing and dynamical heterogeneity between high-density liquid (HDL) and low-density liquid (LDL) silica phases.
Area of Science:
- Materials Science
- Computational Chemistry
- Physical Chemistry
Background:
- Understanding the liquid-liquid phase transition (LLPT) in silica is crucial for materials science.
- Characterizing the silica liquid-liquid interface provides insights into phase behavior beyond bulk properties.
- Previous studies focused on bulk silica LLPT and crystal-melt interfaces, leaving the HDL-LDL interface less explored.
Purpose of the Study:
- To investigate the equilibrium interface between high-density liquid (HDL) and low-density liquid (LDL) silica phases.
- To characterize the structure, thermodynamics, and dynamics within this interfacial region.
- To compare the silica HDL-LDL interface with bulk silica LLPT and traditional crystal-melt interfaces.
Main Methods:
- Molecular-dynamics (MD) simulation was employed to model the silica liquid-liquid interface.
- Detailed analysis of structural, thermodynamic, and dynamic properties was performed.
- Comparison with existing data on bulk silica LLPT and crystal-melt interfaces.
Main Results:
- A spatial fragile-to-strong transition was observed across the silica HDL-LDL interface.
- Three types of dynamical heterogeneity were identified within the interface.
- An unexpected jump in the Si/O coordination number ratio was found, indicating significant mixing in a thin interfacial region.
Conclusions:
- The silica HDL-LDL interface exhibits unique properties distinct from bulk silica and crystal-melt interfaces.
- The interface demonstrates complex dynamical behavior and significant inter-phase mixing.
- The liquid-liquid phase coexistence in silica can be understood using thermodynamic frameworks for alloys and phase equilibria.
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