Stokes-Einstein relation for pure simple fluids.
M Cappelezzo1, C A Capellari, S H Pezzin
1Department of Mathematics, State University of Santa Catarina, Campus Universitário Prof. Avelino Marcante s/n, Joinville 89223-100, Santa Catarina, Brazil.
The Journal of Chemical Physics
|June 22, 2007
Summary
The Stokes-Einstein relation for simple fluids was tested using molecular dynamics simulations. Results show the relation
Area of Science:
- Thermodynamics
- Fluid Dynamics
- Computational Physics
Background:
- The Stokes-Einstein (SE) relation is a fundamental concept in fluid dynamics, linking transport properties like diffusion and viscosity.
- Investigating the SE relation's validity across various fluid states is crucial for understanding molecular behavior.
Purpose of the Study:
- To precisely calculate the constant (alpha) in the SE relation for simple fluids.
- To evaluate the applicability of the classical and modified SE relations under diverse conditions.
- To explore the influence of hydrodynamic radius definitions on SE relation predictions.
Main Methods:
- Equilibrium molecular dynamics simulations were used.
- Calculations were performed for simple fluids obeying the Lennard-Jones 6-12 potential.
- A wide range of temperatures and densities were explored, including hard-sphere systems.
Main Results:
- The constant alpha in the SE relation varies, with values of 4 (slip boundary) and 6 (stick boundary) observed.
- An intermediate alpha value of 5 was found in certain regions, aligning with mode coupling theory predictions.
- Slip boundary conditions were also observed in hard-sphere systems at high densities.
Conclusions:
- The SE relation's validity is state-dependent, with alpha varying based on fluid density, temperature, and hydrodynamic radius definition.
- Simulation results support both slip and stick boundary conditions under specific circumstances.
- Hydrodynamic radius definitions significantly impact the interpretation of SE relation adherence.
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