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An Analog Macroscopic Technique for Studying Molecular Hydrodynamic Processes in Dense Gases and Liquids
Published on: December 4, 2017
Pressure derivatives in the classical molecular-dynamics ensemble.
Karsten Meier1, Stephan Kabelac
1Institut für Thermodynamik, Helmut-Schmidt-Universität - Universität der Bundeswehr Hamburg, Germany. karsten.meier@hsu-hh.de
The Journal of Chemical Physics
|February 18, 2006
Summary
This study refines molecular dynamics simulations for calculating thermodynamic properties. New expressions enable accurate computation of pressure derivatives and fluid properties like compressibility and sound speed.
Area of Science:
- Thermodynamics
- Computational Physics
- Statistical Mechanics
Background:
- Conventional molecular dynamics (MD) simulations face challenges in accurately calculating thermodynamic state variables, especially pressure derivatives.
- Previous work by Lustig and others has provided frameworks but requires refinement for precise calculations.
Purpose of the Study:
- To derive general expressions for phase-space functions and volume derivatives of potential energy within the MD ensemble.
- To enable accurate calculation of thermodynamic state variables, including compressibility and speed of sound.
- To address limitations in previous MD simulation methods for thermodynamic property calculations.
Main Methods:
- Development of general expressions for phase-space functions considering conserved quantities.
- Derivation of correct general expressions for volume derivatives of potential energy.
- Verification through MD simulations of the Lennard-Jones fluid (256 particles) at gas and liquid state points.
Main Results:
- A general expression for phase-space functions accounting for conserved quantities (G) was derived.
- Correct general expressions for volume derivatives of potential energy were obtained, resolving prior issues.
- MD simulations validated the accurate calculation of state variables and pressure derivatives up to second order.
Conclusions:
- The refined MD framework allows for accurate calculation of key thermodynamic properties and pressure derivatives.
- Third- and higher-order pressure derivatives are currently limited by numerical accuracy in MD integration algorithms for systems of this size.
- This work provides a foundation for more precise thermodynamic calculations in molecular dynamics simulations.
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