Energy landscapes for diffusion: analysis of cage-breaking processes

Area of Science:

• Physical Chemistry
• Computational Materials Science

Background:

• Binary Lennard-Jones systems exhibit diverse potential energy barriers.
• Diffusion in such systems is influenced by rearrangements and energy barriers.

Purpose of the Study:

• To investigate energy barriers and cage-breaking rearrangements relevant to long-term diffusion.
• To assess the relationship between cage-breaking events and diffusion in energy landscapes.
• To compare different definitions of cage-breaking processes.

Main Methods:

• Analysis of potential energy barriers in binary Lennard-Jones systems.
• Identification and characterization of single-step cage-breaking processes.
• Utilizing disconnectivity graphs to visualize cage-breaks within the potential energy landscape.
• Comparing productive cage-breaks with existing definitions like 'megabasins' and 'metabasins'.

Main Results:

• Identified single-step cage-breaking processes along high-barrier routes.
• Determined that productive cage-breaks adequately describe diffusion at low temperatures.
• Found that considering all cage-breaks and their reversals also accurately models diffusion.
• Established key parameters for estimating diffusion constants: mean square displacement, average waiting time, and number of reversed cage-breaks.

Conclusions:

• Diffusion in binary Lennard-Jones systems at low temperatures can be accurately described by productive cage-breaks or by accounting for reversals in all cage-breaks.
• The study provides a framework for understanding and quantifying diffusion through energy landscape analysis.
• The findings offer insights into the dynamics of particle rearrangements and their impact on macroscopic diffusion.