@article {48155, title = {Identifying structural signature of dynamical heterogeneity via the local softness parameter}, journal = {Physical Review E}, volume = {105}, year = {2022}, month = {APR}, pages = {044604}, type = {Article}, abstract = {

In this work we study the relationship between the softness of a mean-field caging potential and dynamics at the local level. We first describe the local softness, which shows a distribution, thus identifying structural heterogeneity. We show that the lifetime of the softness parameter is connected to the lifetime of the well-known cage structure in supercooled liquids. Finally, our theory predicts that the local softness and the local dynamics is causal below the onset temperature where there is a decoupling between the short and long time dynamics, thus allowing a static description of the cage. With the decrease in temperature, the correlation between structure and dynamics increases. The study shows that at lower temperatures, the structural heterogeneity increases, and since the structure becomes a better predictor of the dynamics, it leads to an increase in the dynamical heterogeneity. We also find that the softness of a hard, immobile region evolves with time and becomes soft and eventually mobile due to the rearrangements in the neighborhood, confirming the well-known facilitation effect.

}, issn = {2470-0045}, doi = {10.1103/PhysRevE.105.044604}, author = {Sharma, Mohit and Nandi, Manoj Kumar and Bhattacharyya, Sarika Maitra} } @article {48978, title = { Comparative study of the correlation between the structure and the dynamics for systems interacting via attractive and repulsive potentials}, journal = {Journal of Chemical Physics }, volume = {159}, year = {2023}, month = {SEP }, type = {Article}, abstract = {

We present the study of the structure-dynamics correlation for systems interacting via attractive Lennard-Jones (LJ) and its repulsive counterpart, the Weeks-Chandler-Andersen (WCA) potentials. The structural order parameter (SOP) is related to the microscopic mean-field caging potential. At a particle level, the SOP shows a distribution. Although the two systems have similar pair structures, their average SOP differs. However, this difference alone is insufficient to explain the well known slowing down of the dynamics in the LJ system at low temperatures. The slowing down can be explained in terms of a stronger coupling between the SOP and the dynamics. To understand the origin of this system specific coupling, we study the difference in the microscopic structure between the hard and soft particles. We find that for the LJ system, the structural differences of the hard and soft particles are more significant and have a much stronger temperature dependence compared to the WCA system. Thus, the study suggests that attractive interaction creates more structurally different communities. This broader difference in the structural communities is probably responsible for stronger coupling between the structure and dynamics. Thus, the system specific structure-dynamics correlation, which also leads to a faster slowing down in the dynamics, appears to have a structural origin. A comparison of the predictive power of our SOP with the local energy and two body excess entropy in determining the dynamics shows that in the LJ system, the enthalpy plays a dominant role and in the WCA system, the entropy plays a dominant role, and our SOP can capture both these contributions.

}, issn = {0021-9606}, doi = {10.1063/5.0165417}, author = {Sharma, Mohit and Nandi, Manoj Kumar and Bhattacharyya, Sarika Maitra} } @article {48675, title = {Dynamic heterogeneity in polydisperse systems: a comparative study of the role of local structural order parameter and particle size}, journal = {Journal of Chemical Physics}, volume = {159}, year = {2023}, month = {JUL}, pages = {044501}, type = {Article}, abstract = {

In polydisperse systems, describing the structure and any structural order parameter (SOP) is not trivial as it varies with the number of species we use to describe the system, M. Depending on the degree of polydispersity, there is an optimum value of M = M-0 where we show that the mutual information of the system increases. However, surprisingly, the correlation between a recently proposed SOP and the dynamics is highest for M = 1. This effect increases with polydispersity. We find that the SOP at M = 1 is coupled with the particle size, s, and this coupling increases with polydispersity and decreases with an increase in M. Careful analysis shows that at lower polydispersities, the SOP is a good predictor of the dynamics. However, at higher polydispersity, the dynamics is strongly dependent on s. Since the coupling between the SOP and s is higher for M = 1, it appears to be a better predictor of the dynamics. We also study the Vibrality, an order parameter independent of structural information. Compared to SOP, at high polydispersity, we find Vibrality to be a marginally better predictor of the dynamics. However, this high predictive power of Vibrality, which is not there at lower polydispersity, appears to be due to its stronger coupling with s. Therefore, our study suggests that for systems with high polydispersity, the correlation of any order parameter and s will affect the correlation between the order parameter and dynamics and need not project a generic predictive power of the order parameter.

}, issn = {0021-9606}, doi = {10.1063/5.0156794}, author = {Patel, Palak and Sharma, Mohit and Bhattacharyya, Sarika Maitra} } @article {49278, title = {Exploring the soft pinning effect in the dynamics and the structure-dynamics correlation in multicomponent supercooled liquids}, journal = {Journal of Chemical Physics}, volume = {161}, year = {2024}, month = {OCT}, pages = {154501}, type = {Article}, 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{\textquoteright} 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 centers in both high and low-temperature regimes. A key finding is that akin to the pinned system, the self-dynamics 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 centers, the modified quaternary framework predicts a higher correlation.

}, issn = {0021-9606}, doi = {10.1063/5.0230932}, author = {Anwar, Ehtesham and Patel, Palak and Sharma, Mohit and Bhattacharyya, Sarika Maitra} } @article {49234, title = {Structural origin of relaxation in dense colloidal suspensions}, journal = {PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA}, volume = {121}, year = {2024}, month = {OCT }, type = {Journal Article}, keywords = {DEFORMATION, flow, glass-transition, ORDER, SOFT}, issn = {0027-8424}, doi = {10.1073/pnas.2405515121}, author = {Sahu, Ratimanasee and Sharma, Mohit and Schall, Peter and Bhattacharyya, Sarika Maitra and Chikkadi, Vijayakumar} } @article {49895, title = {Growth of structural lengthscale in Kob-Andersen binary mixtures: Role of medium range order}, journal = {Journal of Chemical Physics}, volume = {163}, year = {2025}, month = {NOV }, pages = {204505}, type = {Article}, abstract = {

A central and extensively debated question in glass physics concerns whether a single, growing lengthscale fundamentally controls glassy dynamics, particularly in systems lacking obvious structural motifs such as the Kob-Andersen binary Lennard-Jones (KALJ) model. In this work, we investigate structural and dynamical lengthscales in supercooled liquids using the KALJ model in two compositions: 80:20 and 60:40. We compute the dynamical lengthscale from displacement-displacement correlation functions and observe a consistent growth as temperature decreases. To explore the static counterpart, we use a structural order parameter (SOP) based on the mean field caging potential. While this SOP is known to predict short time dynamics effectively, its bare correlation function reveals minimal spatial growth. Motivated by recent findings that long time dynamics reflect collective rearrangements, we perform spatial coarse-graining of the SOP and identify an optimal lengthscale L-max that maximizes structure-dynamics correlation. We show that the structural correlation length derived from SOP coarse-grained over L-max exhibits clear growth with cooling and closely tracks the dynamical lengthscale, especially for A particles in the 80:20 mixture and for both A and B particles in the 60:40 system. Our results reconcile the previously observed absence of static length growth in the KALJ model by highlighting the necessity of intermediate range structural descriptors. Furthermore, we find that the particles with larger structural length growth also correspond to species with latent crystallization tendencies, suggesting a possible link between structural order, dynamics, and incipient crystallization.

}, issn = {0021-9606}, doi = {10.1063/5.0292633}, author = {Kumawat, Sanket and Sharma, Mohit and Nandi, Ujjwal Kumar and Tah, Indrajit and Bhattacharyya, Sarika Maitra} } @article {49907, title = {Structure-dynamics correlation and its link to fragility and dynamic heterogeneity}, journal = {Journal of Statistical Mechanics-Theory and Experiment}, volume = {2025}, year = {2025}, month = {SEP }, pages = {094005}, type = {Article}, abstract = {

Understanding the connection between structure, dynamics, and fragility, the rate at which the relaxation time grows with the decreasing temperature, is central to unravelling the glass transition. Fragility is often associated with dynamic heterogeneity, implying that if the structure influences the dynamics, more fragile systems should exhibit stronger structure-dynamics correlations. In this study, we test the generality of this assumption using the Lennard-Jones (LJ) and Weeks-Chandler-Andersen systems, where the fragility is tuned via the density, and a modified LJ (q, p) system, where the fragility is varied by changing the potential softness. We define a structural order parameter based on a mean-field caging potential and analyse the energy barriers at both the macroscopic and microscopic levels. While the macroscopic free energy barrier slope correlates with fragility, the microscopic free energy barrier does not show a consistent trend. Instead, it exhibits a strong correlation with a structure-dynamics correlation measure obtained from isoconfigurational ensemble simulations. Interestingly, the two systems showing the highest structure-dynamics correlation, LJ at rho = 1.1 and the (8, 5) model, are respectively the least and most fragile within their classes. These systems exhibit broad mobility distributions and large non-Gaussian parameters but low four-point susceptibilities, suggesting a decoupling between the spatial correlation length and mobility contrast. Both systems lie in the enthalpy-dominated regime and are close to the spinodal, pointing to mechanical instability as a source of heterogeneity. Our results reveal that the structure-dynamics correlation is more closely linked to the contrast in individual particle mobility than to the spatial extent of dynamic correlations that typically scale with fragility.

}, keywords = {dynamical heterogeneities, Glasses, glassy dynamics, slow relaxation, structural}, issn = {1742-5468}, doi = {10.1088/1742-5468/ae012d}, author = {Sharma, Mohit and Sastry, Srikanth and Maitra Bhattacharyya, Sarika} }