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Connectivity in the potential energy landscape for binary Lennard-Jones systems
Vanessa K de Souza1, David J Wales
1University Chemical Laboratories, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom.
The Journal of Chemical Physics
|May 27, 2009
Summary
Understanding cage-breaking events in binary Lennard-Jones systems reveals how system connectivity changes with temperature. Lower temperatures increase reversals, impacting diffusion dynamics and super-Arrhenius behavior.
Area of Science:
- Physical Chemistry
- Computational Chemistry
- Statistical Mechanics
Background:
- Potential energy landscapes are crucial for understanding molecular dynamics.
- Cage-breaking events characterize transitions between local minima in these landscapes.
- Super-Arrhenius behavior is observed in many glassy systems.
Purpose of the Study:
- To characterize connectivity in the potential energy landscape of a binary Lennard-Jones system.
- To determine the relationship between cage-breaking events, temperature, and system connectivity.
- To associate changes in connectivity with super-Arrhenius behavior.
Main Methods:
- Calculating the number of cage-breaking routes from local minima.
- Determining branching probabilities and correlation factors at various temperatures.
- Modeling cage-breaking events as a correlated random walk.
Main Results:
- The number of reversals increases at lower temperatures and in more fragile systems.
- Accessible connections decrease with decreasing temperature.
- Average waiting times within a minimum exhibit simple exponential behavior as temperature decreases.
- Reversals in minimum-to-minimum transitions are frequent but not always cage-breaking.
Conclusions:
- Changes in connectivity are linked to super-Arrhenius behavior.
- Cage-breaking processes are key to understanding diffusion in these systems.
- Correlation factors can be efficiently calculated using short simulations of cage-breaking events.
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