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NVU view on energy polydisperse Lennard-Jones systems
Danqi Lang1, Lorenzo Costigliola1, Jeppe C Dyre1
1Roskilde University, Glass and Time, IMFUFA, Department of Science and Environment, P.O. Box 260, DK-4000 Roskilde, Denmark.
Physical Review. E
|March 19, 2025
Summary
Introducing energy variations into Lennard-Jones systems minimally impacts structure and dynamics. This invariance is linked to a stable constant-potential-energy surface, unlike size variations.
Area of Science:
- Condensed matter physics
- Statistical mechanics
- Computational physics
Background:
- The Lennard-Jones (LJ) system is a fundamental model in physics.
- Polydispersity, the variation in particle properties, can significantly alter system behavior.
- Previous studies suggest size polydispersity strongly affects LJ system dynamics.
Purpose of the Study:
- To investigate the effect of energy polydispersity on the structure and dynamics of Lennard-Jones systems.
- To compare the impact of energy polydispersity with that of size polydispersity.
- To explore the underlying physical reasons for the observed invariance.
Main Methods:
- Simulations of Lennard-Jones systems with up to 30% energy polydispersity.
- Analysis of structural properties using the radial distribution function.
- Evaluation of dynamic properties via mean-square displacement calculations.
- Theoretical analysis based on constant-potential-energy surfaces and NVU dynamics.
Main Results:
- Energy polydispersity has a negligible effect on the radial distribution function and mean-square displacement.
- The structure and dynamics of energy polydisperse LJ systems closely resemble those of single-component LJ systems.
- In contrast, size polydispersity significantly alters the constant-potential-energy surface.
Conclusions:
- The approximate invariance of the constant-potential-energy surface is the key reason for the minimal impact of energy polydispersity.
- NVU (Number-Volume-Energy) dynamics, equivalent to Newtonian dynamics in the thermodynamic limit, explains this phenomenon.
- Energy polydispersity does not fundamentally change the physics of LJ systems, unlike size polydispersity.
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