Single-particle trajectories in supercooled liquids display long periods of localization interrupted by ``fast moves.'' This observation suggests a modeling continuous-time random walk (CTRW). We perform molecular dynamics simulations equilibrated short-chain polymer melts near the critical temperature mode-coupling theory ${T}_{\mathrm{c}}$ and extract ``moves'' from monomer trajectories. show that not all moves comply with conditions CTRW. Strong forward-backward correlations are found...

Abstract Spontaneous mechanical self-assembly of monodisperse bubbles generally leads to disordered foams at low density. Producing crystalline structures requires specific care: for example, Kelvin - periodic assemblies arranged on a body-centered cubic lattice are typical example structure which is challenging obtain experimentally, despite it being local minimum energy. Here we show how bubbling in different arrangements fibers enables control foam architectures through guided bubbles:...

Contrary to common belief, hydrodynamic interactions in polymer melts are not screened beyond the monomer length and important transient regimes. We show that viscoelastic (VHIs) lead anomalous dynamics of a tagged chain an unentangled melt at $t<{t}_{N}$, Rouse time. The center-of-mass (c.m.) mean-square displacement is enhanced by large factor increasing with length. develop theory VHI-controlled yielding negative c.m. velocity autocorrelation function which agrees our molecular...

We present the derivation of coarse-grained force fields for two types polymers, polyethylene (PE), and cis-polybutadiene (cis-PB), using concept potential mean force. Coarse-grained were obtained from microscopic simulations several coarse-graining levels, i.e., different number monomers lambda per mesoscopic unit called "bead." These are then used in dissipative particle dynamics (DPD) to study structural dynamical properties polymer melts PE cis-PB. The radial distribution functions g(R),...

The continuous-time random walk (CTRW) describes the single-particle dynamics as a series of jumps separated by waiting times. This description is applied to analyze trajectories from molecular (MD) simulations supercooled polymer melt. Based on algorithm presented Helfferich et al. [Phys. Rev. E 89, 042603 (2014)], we detect jump events monomers. As function temperature and chain length, examine key distributions CTRW: jump-length distribution (JLD), waiting-time (WTD), persistence-time...

A mode-coupling theory (MCT) version (called hMCT thereafter) of a recently presented [Farago, Meyer, and Semenov, Phys. Rev. Lett. 107, 178301 (2011)] is developed to describe the diffusional properties tagged polymer in melt. The accounts for effect viscoelastic hydrodynamic interactions (VHIs), that is, physical mechanism distinct from density-based MCT (dMCT) described first paper this series. two versions yield different contributions asymptotic behavior center-of-mass velocity...

We quantitatively assess the effect of density fluctuation modes on dynamics a tagged polymer in an unentangled melt. To this end, we develop density-based mode-coupling theory (dMCT) using Mori-Zwanzig approach and projecting fluctuating force onto pair-density modes. The dynamical fluctuations center-of-mass (c.m.) is also analyzed based perturbative show that dMCT perturbation techniques yield identical results. c.m. velocity autocorrelation function (c.m. VAF) exhibits slow power law...

Corrections to chain ideality have been demonstrated recently for polymer melts in the bulk and ultrathin films. It has shown that effect of incomplete screening is stronger latter. We show here deviation from even thin capillaries. Describing crossover free confined regime as radius capillary decreases below typical coil we make connection so far disconnected work by Brochard de Gennes (J. Phys. (Paris), Lett., 40 (1979) 399) predicting segregation very Due generalized Porod scattering...

This paper focuses on the temporal discretization of Langevin dynamics, and different resulting numerical integration schemes. Using a method based exponentiation time dependent operators, we carefully derive scheme for which found equivalent to proposal Ermak Buckholtz [J. Comput. Phys. 35, 169 (1980)] not simply stochastic version velocity-Verlet algorithm. However, checked simulations that both algorithms give similar results, share same “weak order two” accuracy. We then apply strategy...

A quantitative theory of hydrodynamic interactions in unentangled polymer melts and concentrated solutions is presented. The study focussed on the pre-Rouse transient time regimes (t < τ(R), Rouse relaxation time) where response governed mainly by viscoelastic effects. It shown that are not suppressed (screened) at large distances virtually independent molecular mass. number unusual qualitatively different behavior isotropic anisotropic functions elucidated. characterized terms two main...

By Monte Carlo simulations of a variant the bond-fluctuation model without topological constraints we examine center-of-mass (COM) dynamics polymer melts in $d=3$ dimensions. Our analysis focuses on COM displacement correlation function $\CN(t) \approx \partial_t^2 \MSDcmN(t)/2$, measuring curvature mean-square $\MSDcmN(t)$. We demonstrate that -(\RN/\TN)^2 (\rhostar/\rho) \ f(x=t/\TN)$ with $N$ being chain length ($16 \le N 8192$), $\RN\sim N^{1/2}$ typical size, $\TN\sim N^2$ longest...

We introduce a new theoretical model of simple fluid, whose interactions, defined in terms the Voronoi cells configurations, are local and many-body. The resulting system is studied both theoretically numerically. show that though sharing global features other models fluids with soft has several unusual characteristics, which investigated discussed.

The binary Voronoi mixture is a fluid model whose interactions are local and many-body. Here we perform molecular-dynamics (MD) simulations of an equimolar that weakly polydisperse additive. For the first time study structural relaxation this in supercooled-liquid regime. From determine time- temperature-dependent scattering functions for large range wave vectors, as well mean-square displacements both particle species. We detailed analysis dynamics by comparing MD results with...

Due to their unique mechanical and thermal properties, polyurethane foams are widely used in multiple fields of applications, including cushioning, insulation or biomedical engineering. However, the way usually manufactured - via chemical foaming produces samples where blowing gelling occur at same time, resulting a morphology control achieved by trial error processes. Here, novel strategy is introduced build model homogeneous controlled density with millimetric bubbles from liquid...

We develop a fluctuating hydrodynamics approach to study the impact of hydrodynamic and viscoelastic interactions on motion center mass polymer as well relaxation Rouse modes, either in Θ solvent or melt identical unentangled chains. show that this method allows us describe effect beyond Zimm (for single chain solvent) models an melt). In latter case, we recover same important center-of-mass diffusion, first described Farago et al (2011 Phys. Rev. Lett. 107 178301).

The physics of simple fluids in the hydrodynamic limit and notably connection between proper microscopic scales macroscopic hydrodynamical description are nowadays well understood. In particular, three peak shape dynamical structure factor S(k,ω) is a universal feature, as k-dependence position (∝k) width ∝k2, latter accounting for sound attenuation rate. this paper, we present theoretical model monodisperse fluid, whose interactions defined via Voronoi tessellations configurations [called...

We study the effects of vertical sinusoidal vibrations on a liquid droplet with low surface tension (ethanol) deposited solid substrate. In precise range amplitudes and frequencies, drop exhibits dramatic worm-like shape instability strong symmetry breaking, comparable to one observed by Pucci et al. (Phys. Rev. Lett., 106 (2011) 024503) vibrated floating lens. However, geometry our system is much simpler since it does not involve oscillation deformation liquid-liquid-air contact line. show...