arXiv subjects

Jalim Singh

Publications and source records attributed to Jalim Singh.

5 recordsLinked to original sources

arXiv2024

Phase separation in a binary mixture of sticky spheres

We numerically investigate the dependence of range of attractive potential on the phase separation of 2-D binary systems. Through extensive simulations and analysis, we show that when the range of attractive interactions approaches the sticky sphere limit, the system undergoes a phase separation at lower temperature. Further reduction in temperature causes the system to mix again. These mixing-demixing-mixing transitions are of first order. Such phase separation is not observed for systems with larger interaction range. In the phase separated region of the phase diagram, one of the components of the mixture chooses to be in crystalline configuration, while other being in disordered state

physics.comp-ph↗

arXiv2023

Relation between local density and density relaxation near glass transition in a glass forming binary mixture

Many investigations shed light on various correlations between structure and dynamics in supercooled liquids; however, a general relation between structure and dynamics remains elusive. This molecular dynamics simulation study identifies the interrelationship between the growth of the highest peak of the radial distribution function, variation in the radial force from this peak, and the slowdown of the density relaxation in the supercooled states of a model binary glass former. From the microscopic string-like motion in supercooled liquids, we argue that the surface density on a spherical shell around a reference particle at the highest peak of the radial distribution function can represent the free volume available for motion. We further show from these arguments and simulations that density relaxtion time and local density are connected; in this expression, the dynamics diverge at a higher critical value of local density. This relation is similar to the Vogel Fulcher Tammann relation in supercooled liquids, thus giving insight into the structural origin of the VFT as the jamming of particles in a channel of density relaxation.

cond-mat.soft↗

arXiv2021

Super-Arrhenius diffusion in a binary colloidal mixture at low volume fraction: an effect of depletion interaction due to an asymmetric barrier

We report results from the molecular dynamics simulations of a binary colloidal mixture subjected to an external potential barrier along one of the spatial directions at low volume fraction, ϕ = 0.2. The variations in the asymmetry of the external potential barrier do not change the dynamics of the smaller particles, showing Arrhenius diffusion. However, the dynamics of the larger particles shows a crossover from sub-Arrhenius to super-Arrhenius diffusion with the asymmetry in the external potential at the low temperatures and low volume fraction. Super-Arrhenius diffusion is generally observed in the high density systems where the transient cages are present due to dense packing, e.g., supercooled liquids, jammed systems, diffusion through porous membranes, dynamics within the cellular environment, etc. This model can be applied to study the molecular transport across cell membranes, nano-, and micro-channels which are characterized by spatially asymmetric potentials.

cond-mat.soft↗

arXiv2020

Phase separation in a two-dimensional binary colloidal mixture by quorum sensing activity

We present results from Langevin dynamics simulations of a glassy active-passive mixture of soft-repulsive binary colloidal disks. Activity on the smaller particles is applied according to the quorum sensing scheme, in which a smaller particle will be active for a persistence time if its local nearest neighbors are equal to or greater than a certain threshold value. We start with a passive glassy state of the system and apply activity to the smaller particles, which shows a nonmonotonous glassy character of the active particles with the persistence time of the active force, from its passive limit (zero activity). On the other hand, passive particles of the active-passive mixture phase separate at the intermediate persistence time of the active force, resulting in the hexatic-liquid and solid-liquid phases. Thus, our system shows three regimes as active glass, phase separation, and active liquid, as the persistence time increases from its smaller values. We show that the solidlike and hexatic phases consisting of passive large particles are stable due to the smaller momentum transfer from active to passive particles, compared to the higher persistence time where the positional and orientational ordering vanishes. Our model is relevant to active biological systems, where glassy dynamics is present, e.g., bacterial cytoplasm, biological tissues, dense quorum sensing bacteria, and synthetic smart amorphous glasses.

cond-mat.soft↗

arXiv2020

Violation of Stokes-Einstein and Stokes-Einstein-Debye relations in polymers at the gas-supercooled liquid coexistence

Molecular dynamics simulations are performed on a system of model linear polymers to look at the violations of Stokes-Einstein (SE) and Stokes-Einstein-Debye (SED) relations near the mode coupling theory transition temperature $T_c$ at three (one higher and two lower) densities. At low temperatures, both lower density systems show stable gas-supercooled-liquid coexistence whereas the higher density system is homogeneous. We show that monomer density relaxation exhibits SE violation for all three densities, whereas molecular density relaxation shows a weak violation of the SE relation near $T_c$ in both lower density systems. This study identifies disparity in monomer mobility and observation of jumplike motion in the typical monomer trajectories resulting in the SE violations. In addition to the SE violation, a weak SED violation is observed in the gas-supercooled-liquid coexisting domains of the lower densities. Both lower density systems also show a decoupling of translational and rotational dynamics in this polymer system.

cond-mat.soft↗