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05:20
Characterization of Thermal Transport in One-dimensional Solid Materials
Published on: January 26, 2014
Solid/solid phase transitions in confined thin films: a zero temperature approach
H Bock1, K E Gubbins, K G Ayappa
1Department of Chemical Engineering, North Carolina State University, Raleigh, North Carolina 27695-7905, USA. hbock@unity.ncsu.edu
The Journal of Chemical Physics
|April 20, 2005
Summary
This study explores how confining methane thin films between graphite surfaces induces solid/solid phase transitions. Researchers observed new buckled phases and found limitations in using standard order parameters to pinpoint transition locations.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Computational Chemistry
Background:
- Thin films exhibit unique properties due to confinement.
- Understanding phase transitions in confined systems is crucial for materials science.
- Methane confined in nanoscale geometries serves as a model system.
Purpose of the Study:
- To investigate confinement-induced solid/solid phase transitions in methane thin films at zero temperature.
- To identify stable phases and precisely locate phase transitions under varying wall separations.
- To evaluate the effectiveness of 2D order parameters in predicting phase transitions.
Main Methods:
- Density Functional Theory (DFT) calculations were employed.
- A mean-field potential represented graphite surfaces confining the methane film.
- Grand canonical potential density was used to determine stable phases and transition points.
Main Results:
- Observed a series of phases with square and triangular symmetry.
- Identified zig-zag buckling and an asymmetric buckled phase at low wall separations.
- Found that 2D order parameters (Psi(4) and Psi(6)) exhibit unphysical behavior near phase transitions.
Conclusions:
- DFT successfully models confinement-induced phase transitions in methane thin films.
- New buckled phases were identified, consistent with theoretical predictions but previously unobserved.
- Standard 2D order parameters are unreliable for precisely locating phase transitions between square and triangular symmetries in this model.
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