Mass dependence of the Soret coefficient for atomic diffusion in condensed matter

Area of Science:

• Condensed matter physics
• Thermodynamics
• Materials science

Background:

• The Ludwig-Soret effect, particle diffusion driven by thermal gradients, has been studied for over 160 years.
• Existing theories struggle to explain experimental observations at the atomic level.
• A deeper theoretical understanding is needed to resolve experimental puzzles.

Purpose of the Study:

• To derive a new theoretical expression for the Soret coefficient in condensed matter.
• To develop an atomic-level model based on fundamental physical parameters.
• To validate the model's predictions using computational simulations.

Main Methods:

• Development of a single-atom statistical model.
• Expression of Soret coefficient using atomic mass and interaction potential.
• Validation through molecular dynamics simulations.
• Focus on Helium (He) atom diffusion on a graphene sheet.

Main Results:

• A novel expression for the Soret coefficient was derived without empirical parameters.
• The model accurately predicts atomic diffusion behavior under thermal gradients.
• Simulations confirmed the model's validity, particularly for He on graphene.

Conclusions:

• The derived model provides a fundamental understanding of the Soret effect at the atomic scale.
• The Soret effect shows potential for separating Helium-3 (³He) from Helium-4 (⁴He) isotopes.
• This work bridges the gap between theoretical models and experimental observations in diffusion phenomena.