Non-local electron-phonon coupling in atomic scale simulations at room temperature in metals

Area of Science:

• Materials Science
• Computational Physics
• Nuclear Engineering

Background:

• The two temperature model (TTM) is crucial for simulating irradiated metallic crystals beyond the Born-Oppenheimer approximation.
• Understanding heat dissipation dynamics is key to predicting material behavior under irradiation.

Purpose of the Study:

• To investigate the size-dependent behavior of heat spike decrease in the TTM.
• To identify the role of electron conductivity and non-local coupling in thermal relaxation.
• To develop a method for incorporating non-local effects into molecular dynamics simulations.

Main Methods:

• Analysis of heat spike decrease within the TTM under varying thermal heterogeneity sizes.
• Identification of the necessity for non-local coupling to match expected metallic behavior.
• Development and validation of a method to transfer non-local contributions to molecular dynamics.

Main Results:

• Heat dissipation rate in TTM is independent of electron conductivity for thermal heterogeneity sizes smaller than the electron mean free path.
• For larger sizes, heat dissipation is primarily governed by electron conductivity.
• A non-local coupling term is required to ensure relaxation time consistently depends on electron conductivity across all sizes.

Conclusions:

• The standard TTM requires modification with non-local coupling for accurate thermal transport simulations in metals.
• The proposed method successfully transfers non-local contributions, enhancing the predictive power of molecular dynamics simulations.
• The method's transferability was confirmed using gold and nickel, materials with distinct electronic properties.