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Enhancing Entropy and Enthalpy Fluctuations to Drive Crystallization in Atomistic Simulations
Pablo M Piaggi1,2, Omar Valsson2,3, Michele Parrinello2,3
1Theory and Simulation of Materials (THEOS), École Polytechnique Fédérale de Lausanne, c/o USI Campus, Via Giuseppe Buffi 13, CH-6900 Lugano, Switzerland.
Physical Review Letters
|July 22, 2017
Summary
This study introduces novel enthalpic and entropic collective variables to drive crystallization in molecular simulations. These generic variables enable spontaneous and reversible transitions between liquid and solid phases for sodium and aluminum.
Area of Science:
- Materials Science
- Computational Chemistry
- Chemical Physics
Background:
- Crystallization is a critical first-order phase transition from liquid to solid, driven by enthalpy-entropy interplay.
- Simulating crystallization requires effective methods to overcome nucleation barriers and explore phase space.
- Existing methods may impose structural biases, limiting the study of diverse crystalline structures.
Purpose of the Study:
- To develop generic collective variables for driving crystallization in molecular simulations.
- To investigate the spontaneous and reversible transitions between liquid and solid phases.
- To demonstrate the utility of these variables for systems with different crystal structures.
Main Methods:
- Introduction of two collective variables: one enthalpic and one entropic.
- Application of variationally enhanced sampling and well-tempered metadynamics simulations.
- Study of sodium (bcc) and aluminum (fcc) crystallization.
Main Results:
- The proposed collective variables effectively drive crystallization without prejudging the final structure.
- Spontaneous and reversible liquid-solid transformations were observed for both sodium and aluminum.
- The method successfully identified the bcc structure for sodium and the fcc structure for aluminum.
Conclusions:
- The developed enthalpic and entropic collective variables offer a powerful, structure-agnostic approach to simulate crystallization.
- This method enhances the efficiency and reliability of molecular simulations for studying phase transitions.
- The findings have implications for understanding and controlling material solidification processes.
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