Calculation of phase diagrams in the multithermal-multibaric ensemble.

Area of Science:

• Computational materials science
• Physical chemistry
• Statistical mechanics

Background:

• Phase diagrams are crucial for understanding material behavior, but their computational determination is challenging.
• Existing simulation methods struggle to efficiently map large portions of phase diagrams, especially for liquid-solid equilibria.

Purpose of the Study:

• To develop a novel computational method for calculating phase diagrams involving liquid and solid phases.
• To overcome the limitations of current simulation techniques in determining phase equilibria.
• To enable efficient computation of liquid-solid coexistence lines over broad temperature and pressure ranges.

Main Methods:

• Introduction of an order parameter to break rotational symmetry.
• Leveraging a recently developed method to sample the multithermal-multibaric ensemble.
• Utilizing reversible transformations between liquid and solid phases within molecular dynamics simulations.

Main Results:

• Successfully computed liquid-solid coexistence lines for entire regions of temperature and pressure phase diagrams in a single simulation.
• Applied the method to determine the bcc-liquid phase diagram of sodium.
• Characterized the fcc-bcc-liquid phase diagram of aluminum.

Conclusions:

• The proposed method significantly enhances the efficiency of phase diagram calculations.
• This approach provides a powerful tool for exploring phase equilibria in various material systems.
• The technique facilitates a more comprehensive understanding of material phase transitions through simulation.