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Fabrication and Optimization of Type II Silicon Clathrate Films
Published on: October 14, 2025
Structural properties and phase transitions in a silica clathrate
Yunfeng Liang1, Folorunso O Ogundare, Caetano R Miranda
1International School for Advanced Studies (SISSA), Trieste, Italy. y_liang@earth.kumst.kyoto-u.ac.jp
The Journal of Chemical Physics
|February 24, 2011
Summary
Molecular dynamics simulations reveal melanophlogite, a silica polymorph, transforms from crystalline to amorphous states under pressure. Recovery from high pressure may yield a mixed crystalline-amorphous sample.
Area of Science:
- Materials Science
- Mineral Physics
- Computational Chemistry
Background:
- Melanophlogite is a low-pressure silica polymorph with known high-temperature cubic and low-temperature distorted phases.
- Previous studies have investigated its behavior under varying thermodynamic conditions.
Purpose of the Study:
- To investigate the structural and topological changes of melanophlogite under high pressure using molecular dynamics simulations.
- To understand the transition from crystalline to amorphous states and predict potential recovery outcomes.
Main Methods:
- Molecular dynamics (MD) simulations were employed to study melanophlogite.
- Simulations covered a range of temperatures and pressures, focusing on the effects of increasing pressure.
- Analysis included radial distribution functions and coordination number changes to characterize structural transformations.
Main Results:
- The high-temperature cubic phase and low-temperature distorted phase were confirmed.
- Increasing pressure leads to a gradual loss of crystalline character, with an amorphous state observed at 8 GPa.
- Above approximately 12 GPa, topological changes, plastic behavior, and permanent densification occur, linked to changes in silicon coordination.
Conclusions:
- Melanophlogite transitions to an amorphous state under high pressure.
- The amorphous transition is driven by changes in Si coordination number.
- A partial crystalline and amorphous sample of melanophlogite is predicted to be obtainable upon recovery from pressures of 12-16 GPa.
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