@article { ISI:000381384300030, title = {Effect of total and pair configurational entropy in determining dynamics of supercooled liquids over a range of densities}, journal = {Journal of Chemical Physics}, volume = {145}, number = {3}, year = {2016}, month = {JUL}, pages = {Article Number: 034502}, publisher = {AMER INST PHYSICS}, address = {1305 WALT WHITMAN RD, STE 300, MELVILLE, NY 11747-4501 USA}, abstract = {

In this paper, we present a study of supercooled liquids interacting with the Lennard Jones potential and the corresponding purely repulsive (Weeks-Chandler-Andersen) potential, over a range of densities and temperatures, in order to understand the origin of their different dynamics in spite of their structures being similar. Using the configurational entropy as the thermodynamic marker via the Adam Gibbs relation, we show that the difference in the dynamics of these two systems at low temperatures can be explained from thermodynamics. At higher densities both the thermodynamical and dynamical difference between these model systems decrease, which is quantitatively demonstrated in this paper by calculating different parameters. The study also reveals the origin of the difference in pair entropy despite the similarity in the structure. Although the maximum difference in structure is obtained in the partial radial distribution function of the B type of particles, the rdf of AA pairs and AB pairs gives rise to the differences in the entropy and dynamics. This work supports the observation made in an earlier study [A. Banerjee et al., Phys. Rev. Lett. 113, 225701 (2014)] and shows that they are generic in nature, independent of density. Published by AIP Publishing.

}, issn = {0021-9606}, doi = {10.1063/1.4958627}, author = {Banerjee, Atreyee and Nandi, Manoj Kumar and Sastry, Srikanth and Bhattacharyya, Sarika Maitra} } @article {47100, title = {Effective structure of a system with continuous polydispersity}, journal = {Journal of Chemical Physics}, volume = {154}, year = {2021}, month = {JAN }, pages = {034503}, type = {Article}, abstract = {

In a system of N particles, with continuous size polydispersity, there exists an N(N - 1) number of partial structure factors, making it analytically less tractable. A common practice is to treat the system as an effective one component system, which is known to exhibit an artificial softening of the structure. The aim of this study is to describe the system in terms of M pseudospecies such that we can avoid this artificial softening but, at the same time, have a value of M \<\< N. We use potential energy and pair excess entropy to estimate an optimum number of species, M-0. We then define the maximum width of polydispersity, Delta sigma (0), that can be treated as a monodisperse system. We show that M-0 depends on the degree and type of polydispersity and also on the nature of the interaction potential, whereas Delta sigma (0) weakly depends on the type of polydispersity but shows a stronger dependence on the type of interaction potential. Systems with a softer interaction potential have a higher tolerance with respect to polydispersity. Interestingly, M-0 is independent of system size, making this study more relevant for bigger systems. Our study reveals that even 1\% polydispersity cannot be treated as an effective monodisperse system. Thus, while studying the role of polydispersity by using the structure of an effective one component system, care must be taken in decoupling the role of polydispersity from that of the artificial softening of the structure.

}, issn = {0021-9606}, doi = {10.1063/5.0038812}, author = {Patel, Palak and Nandi, Manoj Kumar and Nandi, Ujjwal Kumar and Bhattacharyya, Sarika Maitra} } @article {47415, title = {Emergence of cooperatively reorganizing cluster and super-Arrhenius dynamics of fragile supercooled liquids}, journal = {Physical Review E}, volume = {103}, year = {2021}, month = {MAR}, pages = {032611}, type = {Article}, abstract = {

In this paper, we develop a theory to calculate the structural relaxation time tau(alpha) of fragile supercooled liquids. Using the information of the configurational entropy and structure, we calculate the number of dynamically free, metastable, and stable neighbors around a central particle. In supercooled liquids, the cooperatively reorganizing clusters (CRCs) in which the stable neighbors form {\textquoteleft}{\textquoteleft}stable{\textquoteright}{\textquoteright} nonchemical bonds with the central particle emerge. For an event of relaxation to take place, these bonds have to reorganize irreversibly; the energy involved in the processes is the effective activation energy of relaxation. The theory brings forth a temperature T-a and a temperature-dependent parameter psi(T) which characterize slowing down of dynamics on cooling. It is shown that the value of psi(T) is equal to 1 for T \> T-a, indicating that the underlying microscopic mechanism of relaxation is dominated by the entropy-driven processes, while for T \< T-a, psi(T ) decreases on cooling, indicating the emergence of the energy-driven processes. This crossover of psi(T) from high to low temperatures explains the crossover seen in tau(alpha). The dynamics of systems that may have similar static structure but very different dynamics can be understood in terms of psi(T). We present results for the Kob-Anderson model for three densities and show that the calculated values of tau(alpha) are in excellent agreement with simulation values for all densities. We also show that when psi(T), tau(alpha), and other quantities are plotted as a function of T/T-a, (or Ta/T), the data collapse on master curves.

}, issn = {2470-0045}, doi = {10.1103/PhysRevE.103.032611}, author = {Singh, Ankit and Bhattacharyya, Sarika Maitra and Singh, Yashwant} } @article {49029, title = {Effect of the presence of pinned particles on the structural parameters of a liquid and correlation between structure and dynamics at the local level}, journal = {Journal of Chemical Physics}, volume = {160}, year = {2024}, month = {APR }, type = {Article}, abstract = {

Pinning particles at the equilibrium configuration of the liquid is expected not to affect the structure and any property that depends on the structure while slowing down the dynamics. This leads to a breakdown of the structure dynamics correlation. Here, we calculate two structural quantities: the pair excess entropy, S-2, and the mean field caging potential, the inverse of which is our structural order parameter (SOP). We show that when the pinned particles are treated the same way as the mobile particles, both S-2 and SOP of the mobile particles remain the same as those of the unpinned system, and the structure dynamics correlation decreases with an increase in pinning density, {\textquoteleft}{\textquoteleft}c.{\textquoteright}{\textquoteright} However, when we treat the pinned particles as a different species, even if we consider that the structure does not change, the expression of S-2 and SOP changes. The microscopic expressions show that the interaction between a pinned particle and a mobile particle affects S-2 and SOP more than the interaction between two mobile particles. We show that a similar effect is also present in the calculation of the excess entropy and is the primary reason for the well-known vanishing of the configurational entropy at high temperatures. We further show that, contrary to the common belief, the pinning process does change the structure. When these two effects are considered, both S-2 and SOP decrease with an increase in {\textquoteleft}{\textquoteleft}c,{\textquoteright}{\textquoteright} and the correlation between the structural parameters and the dynamics continues even for higher values of {\textquoteleft}{\textquoteleft}c.{\textquoteright}{\textquoteright}

}, issn = {0021-9606}, doi = {10.1063/5.0191680}, author = {Patel, Palak 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} }