Disorder induced melting and glass formation in a one-component Lennard-Jones system

TL;DR

This study uses molecular dynamics simulations to explore how pinning particles in a 2D Lennard-Jones liquid influences its structural and dynamical properties, revealing conditions that prevent crystallization and promote glass formation.

Contribution

It introduces a systematic investigation of pinning effects on 2D Lennard-Jones liquids, highlighting how moderate pinning can inhibit crystallization and alter dynamics.

Findings

Moderate pinning prevents crystallization and enhances particle mobility.

High pinning concentration suppresses dynamics and reduces mobility.

Results align with experimental observations in colloidal suspensions.

Abstract

Identifying the conditions under which glass formation occurs is crucial for a fundamental understanding of the glass transition mechanism. Pure liquids devoid of any frustration avoid glass transition and undergo crystallization. In this work, we investigate a one-component liquid interacting via the Lennard-Jones potential in two dimensions, where disorder is introduced through pinning, a protocol in which a fixed fraction of particles is immobilized at positions selected from an equilibrium configuration. By employing molecular dynamics simulation, we systematically study the influence of pinning concentration on both structural and dynamical properties. Structural properties quantified by radial distribution function and hexatic-order parameter display a systematic decrease with a rise in pinning concentration. However, the dynamical properties such as the fragility index and the late-time mean squared displacement exhibit a non-monotonic trend as the concentration of pinned particles increases. A moderate concentration of pinned particles helps prevent crystallization and facilitates particle motion. A further rise in the number of pinned particles suppresses particle mobility, leading to a reduction in the overall dynamics of the system. These simulation results are in good agreement with experimental observations on colloidal suspensions confined between glass coverslips, where particles are immobilized. Our findings demonstrate the pivotal role of pinning in controlling the phase behavior of simple liquids and validate the unique dynamical features of two-dimensional liquids with pinned particles.