Particle rearrangements during transitions between local minima of the potential energy landscape of a supercooled Lennard-Jones liquid

TL;DR

This study investigates particle rearrangements and string-like motions during transitions between local minima in the potential energy landscape of a supercooled Lennard-Jones liquid, revealing heterogeneity and mechanisms facilitating relaxation.

Contribution

It provides new insights into the spatial heterogeneity and string-like motion mechanisms during inherent structure and meta-basin transitions near the mode-coupling temperature.

Findings

Particle rearrangements are similar during IS and MB transitions near T_MCT.

Rearrangements are spatially heterogeneous and involve string-like motion.

Different groups of particles are active during successive MB transitions.

Abstract

The potential energy landscape (PEL) of supercooled binary Lennard-Jones (BLJ) mixtures exhibits local minima, or inherent structures (IS), which are organized into meta-basins (MB). We study the particle rearrangements related to transitions between both successive IS and successive MB for a small 80:20 BLJ system near the mode-coupling temperature T_MCT. The analysis includes the displacements of individual particles, the localization of the rearrangements and the relevance of string-like motion. We find that the particle rearrangements during IS and MB transitions do not change significantly at T_MCT. Further, it is demonstrated that IS and MB dynamics are spatially heterogeneous and facilitated by string-like motion. To investigate the mechanism of string-like motion, we follow the particle rearrangements during suitable sequences of IS transitions. We find that most strings observed after a series of transitions do not move coherently during a single transition, but subunits of different sizes are active at different times. Several findings suggest that the occurrence of a successful string enables the system to exit a MB. Moreover, we show that the particle rearrangements during two consecutive MB transitions are basically uncorrelated. Specifically, different groups of particles are highly mobile during subsequent MB transitions. Finally, the relation between the features of the PEL and the relaxation processes in supercooled liquids is discussed.