02652nas a2200181   4500008004100000022001400041245010500055210006900160260008700229300002700316490000800343520189300351100002502244700002202269700002302291700003402314856012202348       2016                        eng d  a0021-960600aComposition dependence of the glass forming ability in binary mixtures: the role of demixing entropy0 aComposition dependence of the glass forming ability in binary mi  a1305 WALT WHITMAN RD, STE 300, MELVILLE, NY 11747-4501 USAbAMER INST PHYSICScJUL  aArticle Number: 0345030 v1453 a<p>We present a comparative study of the glass forming ability of binary systems with varying composition, where the systems have similar global crystalline structure (CsCl+fcc). Biased Monte Carlo simulations using umbrella sampling technique show that the free energy cost to create a CsCl nucleus increases as the composition of the smaller particles is decreased. We find that systems with comparatively lower free energy cost to form CsCl nucleus exhibit more pronounced pre-crystalline demixing near the liquid/crystal interface. The structural frustration between the CsCl and fcc crystal demands this demixing. We show that closer to the equimolar mixture, the entropic penalty for demixing is lower and a glass forming system may crystallize when seeded with a nucleus. This entropic penalty as a function of composition shows a non-monotonic behaviour with a maximum at a composition similar to the well known Kob-Anderson (KA) model. Although the KA model shows the maximum entropic penalty and thus maximum frustration against CsCl formation, it also shows a strong tendency towards crystallization into fcc lattice of the larger ``A'' particles which can be explained from the study of the energetics. Thus for systems closer to the equimolar mixture although it is the requirement of demixing which provides their stability against crystallization, for KA model it is not demixing but slow dynamics and the presence of the ``B'' particles make it a good glass former. The locally favoured structure around ``B'' particles is quite similar to the CsCl structure and the incompatibility of CsCl and fcc hinders the fcc structure growth in the KA model. Although the glass forming binary systems studied here are quite similar, differing only in composition, we find that their glass forming ability cannot be attributed to a single phenomenon. Published by AIP Publishing.</p>1 aNandi, Ujjwal, Kumar1 aBanerjee, Atreyee1 aChakrabarty, Suman1 aBhattacharyya, Sarika, Maitra  uhttps://library.ncl.res.in/content/composition-dependence-glass-forming-ability-binary-mixtures-role-demixing-entropy01641nas a2200169   4500008004100000022001400041245008500055210006900140260000900209300001100218490000800229520104300237100002201280700002501302700003401327856011001361       2017                        eng d  a0021-960600aFickian yet non-Gaussian behaviour: A dominant role of the intermittent dynamics0 aFickian yet nonGaussian behaviour A dominant role of the intermi  cAPR   a1345040 v1463 a<p>We present a study of the dynamics of small solute particles in a solvent medium where the solute is much smaller in size, mimicking the diffusion of small particles in crowded environment. The solute exhibits Fickian diffusion arising from non-Gaussian Van Hove correlation function. Our study shows that there are at least two possible origins of this non-Gaussian behaviour: the decoupling of the solute-solvent dynamics and the intermittency in the solute motion, the latter playing a dominant role. In the former scenario when averaged over time long enough to explore different solvent environments, the dynamics recovers the Gaussian nature. In the case of intermittent dynamics the non-Gaussianity remains even after long averaging and the Gaussian behaviour is obtained at a much longer time. Our study further shows that only for an intermediate attractive solute-solvent interaction the dynamics of the solute is intermittent. The intermittency disappears for weaker or stronger attractions. Published by AIP Publishing.</p>1 aAcharya, Sayantan1 aNandi, Ujjwal, Kumar1 aBhattacharyya, Sarika, Maitra  uhttps://library.ncl.res.in/content/fickian-yet-non-gaussian-behaviour-dominant-role-intermittent-dynamics00580nas a2200133   4500008004100000245010900041210006900150260000800219490000800227100002200235700002500257700003400282856013000316       2019                        eng d00aFickian yet non-Gaussian behaviour: A dominant role of the intermittent dynamics (vol 146, 134504, 2017)0 aFickian yet nonGaussian behaviour A dominant role of the intermi  cAUG0 v1511 aAcharya, Sayantan1 aNandi, Ujjwal, Kumar1 aBhattacharyya, Sarika, Maitra  uhttps://library.ncl.res.in/content/fickian-yet-non-gaussian-behaviour-dominant-role-intermittent-dynamics-vol-146-134504-201701954nas a2200169   4500008004100000022001400041245004900055210004800104260000800152300001100160490000800171520144900179100002501628700001601653700003401669856008101703       2021                        eng d  a0021-960600aConnecting real glasses to mean-field models0 aConnecting real glasses to meanfield models  cMAR  a0945060 v1543 a<p>We propose a novel model for a glass-forming liquid, which allows us to switch in a continuous manner from a standard three-dimensional liquid to a fully connected mean-field model. This is achieved by introducing k additional particle-particle interactions, which thus augments the effective number of neighbors of each particle. Our computer simulations of this system show that the structure of the liquid does not change with the introduction of these pseudo-neighbors and by means of analytical calculations, and we determine the structural properties related to these additional neighbors. We show that the relaxation dynamics of the system slows down very quickly with the increase in k and that the onset and the mode-coupling temperatures increase. The systems with high values of k follow the mode-coupling theory power law behavior for a larger temperature range compared to the ones with lower values of k. The dynamic susceptibility indicates that the dynamic heterogeneity decreases with the increase in k, whereas the non-Gaussian parameter is independent of it. Thus, we conclude that with the increase in the number of pseudo-neighbors, the system becomes more mean-field-like. By comparing our results with previous studies on mean-field-like systems, we come to the conclusion that the details of how the mean-field limit is approached are important since they can lead to different dynamical behavior in this limit.</p>
1 aNandi, Ujjwal, Kumar1 aKob, Walter1 aBhattacharyya, Sarika, Maitra  uhttps://library.ncl.res.in/content/connecting-real-glasses-mean-field-models02091nas a2200181   4500008004100000022001400041245006700055210006700122260000900189300001100198490000800209520150000217100001701717700002401734700002501758700003401783856009201817       2021                        eng d  a0021-960600aEffective structure of a system with continuous polydispersity0 aEffective structure of a system with continuous polydispersity  cJAN   a0345030 v1543 a<p>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 &lt;&lt; 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.</p>
1 aPatel, Palak1 aNandi, Manoj, Kumar1 aNandi, Ujjwal, Kumar1 aBhattacharyya, Sarika, Maitra  uhttps://library.ncl.res.in/content/effective-structure-system-continuous-polydispersity02481nas a2200241   4500008004100000022001400041245016600055210006900221260000900290300001100299490000800310520158300318100002501901700001701926700001501943700002401958700002501982700002302007700002202030700002202052700003402074856013102108       2022                        eng d  a0021-960600aThermodynamics and its correlation with dynamics in a mean-field model and pinned systems: a comparative study using two different methods of entropy calculation0 aThermodynamics and its correlation with dynamics in a meanfield   cJAN   a0145030 v1563 aA recent study introduced a novel mean-field model system where each particle over and above the interaction with its regular neighbors interacts with k extra pseudo-neighbors. Here, we present an extensive study of thermodynamics and its correlation with the dynamics of this system. We surprisingly find that the well-known thermodynamic integration (TI) method of calculating the entropy provides unphysical results. It predicts vanishing of the configurational entropy at temperatures close to the onset temperature of the system and negative values of the configurational entropy at lower temperatures. Interestingly, well below the temperature at which the configurational entropy vanishes, both the collective and the single-particle dynamics of the system show complete relaxation. Negative values of the configurational entropy are unphysical, and complete relaxation when the configurational entropy is zero violates the prediction of the random first-order transition theory (RFOT). However, the entropy calculated using the two-phase thermodynamics (2PT) method remains positive at all temperatures for which we can equilibrate the system, and its values are consistent with RFOT predictions. We find that with an increase in k, the difference in the entropy computed using the two methods increases. A similar effect is also observed for a system where a randomly selected fraction of the particles are pinned in their positions in the equilibrated liquid. We show that the difference in entropy calculated via the 2PT and TI methods increases with pinning density.1 aNandi, Ujjwal, Kumar1 aPatel, Palak1 aMoid, Mohd1 aNandi, Manoj, Kumar1 aSengupta, Shiladitya1 aKarmakar, Smarajit1 aMaiti, Prabal, K.1 aDasgupta, Chandan1 aBhattacharyya, Sarika, Maitra  uhttps://library.ncl.res.in/content/thermodynamics-and-its-correlation-dynamics-mean-field-model-and-pinned-systems-comparative02471nas a2200193   4500008004100000022001400041245008300055210006900138260000900207300001100216490000800227520182000235100002002055700002502075700001702100700002002117700003402137856010602171       2025                        eng d  a0021-960600aDynamic signature of the thermodynamic transition in a novel mean field system0 aDynamic signature of the thermodynamic transition in a novel mea  cAUG   a0845100 v1633 a<p>
	Understanding the connection between thermodynamics and dynamics in glass-forming liquids remains a central challenge in condensed matter physics. In this study, we investigate a novel model system that enables a continuous crossover from a standard three dimensional liquid to a fully connected mean field like system by introducing pseudo neighbors. These pseudo neighbors enhance the effective connectivity of the system without altering its local structure. While their presence slows down the dynamics, they influence thermodynamic properties even more significantly. In particular, the configurational entropy obtained via thermodynamic integration vanishes at a temperature much higher than the temperature where the dynamics begin to slow down, leading to a clear breakdown of the Adam-Gibbs relation. To uncover a possible dynamical signature of this thermodynamic transition, we analyze bond breakage dynamics. Unlike real-real bonds, which decay similarly in both the parent Kob-Andersen model and its mean field variant, real-pseudo bonds exhibit long lived, persistent behavior with strong temperature dependence. These bonds do not fully decay over time, leading to a finite saturation value of the bond breakage correlation function. Remarkably, we show that the number of surviving pseudo bonds can be analytically estimated and correlates directly with the thermodynamic transition temperature T-K. We propose a phenomenological relation between T-K and the number of surviving pseudo-bonds, establishing a novel link between thermodynamic and dynamic observables. Our results suggest that these persistent pseudo bonds serve as a robust dynamical signature of the thermodynamic transition, and the system might have properties analogous to those of randomly bonded ultrastable glasses.</p>
1 aAnwar, Ehtesham1 aNandi, Ujjwal, Kumar1 aPatel, Palak1 aKumawat, Sanket1 aBhattacharyya, Sarika, Maitra  uhttps://library.ncl.res.in/content/dynamic-signature-thermodynamic-transition-novel-mean-field-system02411nas a2200193   4500008004100000022001400041245009700055210006900152260000900221300001100230490000800241520173100249100002001980700001802000700002502018700001802043700003402061856012202095       2025                        eng d  a0021-960600aGrowth of structural lengthscale in Kob-Andersen binary mixtures: Role of medium range order0 aGrowth of structural lengthscale in KobAndersen binary mixtures   cNOV   a2045050 v1633 a<p>
	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.</p>
1 aKumawat, Sanket1 aSharma, Mohit1 aNandi, Ujjwal, Kumar1 aTah, Indrajit1 aBhattacharyya, Sarika, Maitra  uhttps://library.ncl.res.in/content/growth-structural-lengthscale-kob-andersen-binary-mixtures-role-medium-range-order