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Analyzing Melts and Fluids from Ab Initio Molecular Dynamics Simulations with the UMD Package
Published on: September 17, 2021
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Bulk viscosity of molecular fluids.
Frederike Jaeger1, Omar K Matar2, Erich A Müller2
1Department of Physics, Imperial College London, London SW7 2AZ, United Kingdom.
The Journal of Chemical Physics
|May 10, 2018
Summary
Molecular simulations reveal bulk viscosity arises from internal degrees of freedom and intermolecular interactions. The configurational contribution dominates, especially near critical points.
Area of Science:
- Physical Chemistry
- Computational Chemistry
- Fluid Dynamics
Background:
- Bulk viscosity in gases and liquids is influenced by molecular behavior.
- Understanding these contributions is crucial for accurate fluid modeling.
Purpose of the Study:
- To determine the bulk viscosity of molecular models.
- To differentiate between dilute gas and configurational contributions.
- To assess force field accuracy for water, CO2, and n-decane.
Main Methods:
- Molecular dynamics simulations using Green-Kubo relations.
- Analysis of pressure tensor fluctuations.
- Incorporation of experimental relaxation time data.
Main Results:
- Dilute gas contribution is significant only for specific relaxation times and low vibrational wave numbers (e.g., CO2).
- Configurational contribution is dominant in most studied cases.
- Lennard-Jones fluid, water, CO2, and n-decane models were benchmarked.
Conclusions:
- Configurational effects are key to bulk viscosity, particularly near critical points.
- Accurate force fields are essential for predicting bulk viscosity.
- The study explains high bulk viscosity in CO2 due to its specific molecular properties.
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