Diagnosing broken ergodicity using an energy fluctuation metric.

Area of Science:

• Condensed Matter Physics
• Computational Chemistry
• Materials Science

Background:

• Understanding the ergodicity of supercooled liquids and glassy states is crucial for accurately calculating diffusion constants.
• Traditional methods for assessing ergodicity can be unreliable, especially at different energy levels.
• The Mountain and Thirumalai energy fluctuation metric, Omega(t), offers a novel approach to quantify ergodicity.

Purpose of the Study:

• To investigate the effective ergodicity of binary Lennard-Jones mixtures using the Omega(t) metric.
• To determine the reliability of diffusion constants calculated at various energies.
• To establish a more appropriate method for identifying ergodic and nonergodic states.

Main Methods:

• Simulation of 60- and 256-atom binary Lennard-Jones mixtures.
• Application of the Mountain and Thirumalai energy fluctuation metric, Omega(t).
• Analysis of Omega(t) behavior over time to identify distinct ergodic and nonergodic regimes.

Main Results:

• Two distinct regimes were identified: ergodic supercooled liquids (Omega(t) approaches zero) and nonergodic glassy states (Omega(t) approaches a nonzero value).
• The Omega(t) metric provides a more suitable approach than threshold-based methods.
• Calculated diffusion constants were observed to change as systems approached effective ergodicity, aligning with higher-energy systems.

Conclusions:

• The Omega(t) metric effectively characterizes the ergodicity of binary Lennard-Jones mixtures.
• This approach enhances the reliability of diffusion constant calculations.
• The study successfully reproduced trends in system fragility, refining previous findings.