Exploring the soft pinning effect in the dynamics and the structure dynamics correlation in multicomponent supercooled liquids

TL;DR

This study investigates how increasing the mass of a subset of particles in a multicomponent supercooled liquid affects their dynamics and structure, revealing temperature-dependent coupling effects and the role of heavy particles as soft pinning centers.

Contribution

It introduces a detailed analysis of soft pinning effects in multicomponent liquids by varying particle mass and compares structural dynamics correlations with modified frameworks.

Findings

Heavy particles decouple from lighter particles at high temperatures.

Increased heavy particle mass enhances their role as soft pinning centers.

Modified quaternary framework better predicts correlations when heavy particles act as pinning centers.

Abstract

We study multicomponent liquids by increasing the mass of $15\%$ of the particles in a binary Kob-Andersen model. We find that the heavy particles have dual effects on the lighter particles. At higher temperatures, there is a significant decoupling of the dynamics between heavier and lighter particles, with the former resembling a pinned particle to the latter. The dynamics of the lighter particles slow down due to the excluded volume around the nearly immobile heavier particles. Conversely, at lower temperatures, there is a coupling between the dynamics of the heavier and lighter particles. The heavier particles' mass slows down the dynamics of both types of particles. This makes the soft pinning effect of the heavy particles questionable in this regime. We demonstrate that as the mass of the heavy particles increases, the coupling of the dynamics between the lighter and heavier particles weakens. Consequently, the heavier the mass of the heavy particles, the more effectively they act as soft pinning centres in both high and low-temperature regimes. A key finding is that akin to the pinned system, the self and collective dynamics of the lighter particles decouple from each other as the mass of the heavy particles has a more pronounced impact on the latter. We analyze the structure dynamics correlation by considering the system under the binary and modified quaternary framework, the latter describing the pinned system. Our findings indicate that whenever the heavy mass particles function as soft pinning centres, the modified quaternary framework predicts a higher correlation.