Self-diffusion rates in Al from combined first-principles and model-potential calculations

Area of Science:

• Materials Science
• Condensed Matter Physics
• Computational Materials Science

Background:

• Understanding atomic diffusion mechanisms is crucial for predicting material properties.
• Previous models often simplified diffusion processes, potentially overlooking key factors at various temperatures.

Purpose of the Study:

• To determine the dominant atomic diffusion mechanism in aluminum (Al).
• To investigate the reasons for deviations from a single Arrhenius dependence in diffusion.
• To validate theoretical predictions against experimental diffusion rates.

Main Methods:

• Utilized a combination of theoretical methods, including density functional theory (DFT).
• Employed thermodynamic integration for advanced calculations.
• Calculations were performed without fitting to experimental data.

Main Results:

• Monovacancy diffusion was identified as the dominant mechanism in Al, surpassing divacancy and interstitial diffusion.
• Anharmonicity in the material was identified as the cause for deviations from a single Arrhenius behavior.
• Theoretical diffusion rates showed excellent agreement with experimental data over 11 orders of magnitude.

Conclusions:

• Monovacancy diffusion solely governs atomic transport in Al up to its melting point.
• Material anharmonicity is responsible for observed deviations in diffusion behavior.
• The theoretical approach provides a reliable, data-driven method for predicting diffusion rates.