We present coarse-grained molecular dynamics simulations of linear polyethylene (PE) melts, ranging in chain length from C80 to C1000. The employed effective potentials, frictions, and random forces are all derived detailed simulations, leaving no adjustable parameters. Uncrossability constraints introduced the model prevent unphysical bond crossings. dynamic zero-shear rate rheological properties investigated compared with experiment other simulation work. In analysis internal relaxations...

An important feature of a melt long polymers is that the bonds chains cannot cross each other. This seemingly simple fact has great impact on time dynamics and rheology material. In this paper an algorithm described explicitly detects prevents bond crossings in mesoscopic simulations polymers. The central idea to view as slippery elastic bands which can become entangled. method applied simulation coarse-grained C120H242, chain represented by six blobs. zero-shear rate are investigated...

Atomistic molecular dynamics simulations of a lipid bilayer were performed to calculate the free energy trans-membrane pore as function its radius. The was calculated reaction coordinate using potential mean constraint force. radius then from Monte Carlo particle insertions. main characteristics that comes out are quadratic shape for less than about 0.3 nm, linear larger radii this, and rather abrupt change without local minima or maxima between two regions. In outer region, line tension can...

Abstract The rich phase behavior of granular beds bidisperse hard spherical particles in a rotating horizontal drum is studied by Discrete Element Method (DEM) simulations. Several flow regimes and various forms radial segregation, as well mixing, are observed systematically varying the operational parameters drum, i.e. fill level angular velocity, over wide range. Steady states after several dozen revolutions summarized two bed diagrams, showing strong correlations between regime...

In this paper we set out to derive a relation between the constraint force and derivative of free energy for system in which only reaction coordinate is constrained. Our result differs from expression by Mülders et al. [J. Chem. Phys. 104, 4869 (1996)] because take into account effect on sampled phase-space distribution. The method illustrated with two prototypical numerical examples.

In this study we explore a systematic procedure to coarsen microscopic model towards mesoscopic model. The is applied system of chains ten beads, representing low molecular weight polymer melt. Our method consists defining coarse-grained sites in the system, and calculating their spatial distribution on pair level. effective interaction between then obtained by bringing consistence with density. We investigate both dynamic stochastic for step. so used dynamics simulation pressure system....

The impact of particle properties on segregation and mixing bidisperse granular beds in a rotating horizontal drum have been studied by discrete element method (DEM) simulations. Bidispersities radius, density, mass pronounced influences the stationary pattern, although they hardly affect granules' flow regime. At 50% fill level, all mix well for Froude number ∼0.56, corresponding to regime intermediate cascading cataracting, while occurs both at lower (rolling regime) higher...

Amphiphilic bilayers with a pore were simulated using coarse grained model. By stretching the bilayer to 70% beyond its equilibrium surface area, we established phase diagram of pores, identifying regions where pores are stable, metastable, or unstable. A simple theoretical model is proposed explain diagram, and calculate critical relative stretches. Interestingly, these found scale inverse cubic root number amphiphiles in bilayer, thus explaining order magnitude difference between measured...

In this study we present the coarse-graining of one polymer chain in a melt to single dimer. By using projector operator formalism derive equation motions for The different forces that occur motion are calculated from molecular dynamics simulations microscopic model, constraint fix dimer configuration. mean force serves as conserved part interaction, whereas time correlation fluctuation leads nonconserved interactions: dissipative and fluctuating forces. Using configurational dependent...

The formation of a pore in membrane requires considerable rearrangement the amphiphilic molecules about to form bilayer edge surrounding pore, and hence is accompanied by steep increase free energy. Recent rupture conductance experiments suggest that this reshuffling process also responsible for small energy barrier stabilizes "prepores" with diameters less than 1 nm, rendering both opening closing pores an activated process. We use potential mean constraint force method study profile, as...

Helfrich’s theory predicts that the bending free energy of a tensionless amphiphilic bilayer is proportional to square Fourier coefficients undulation modes. Equilibrium molecular dynamics simulations with coarse-grained amphiphiles confirm correctness this prediction for thermally excited undulations. The proportionality constant then provides rigidity layer. Non-equilibrium methods, in particular umbrella sampling, potential mean constraint force, and thermodynamic integration Cartesian...

Flat clathrin lattices or 'plaques' are commonly believed to be the precursors clathrin-coated buds and vesicles. The sequence of steps carrying flat hexagonal lattice into a highly curved polyhedral cage with exactly 12 pentagons remains elusive, however, large numbers disrupted interclathrin connections in previously proposed conversion pathways make these scenarios rather unlikely. recent notion that can controlled small conformational transitions opens new avenues. Simulations...

We studied unentangled poly(ethylene-alt-propylene) (PEP) in a composite with hydrophobic silica particles as function of the filler concentration. Our neutron spin echo (NSE) experiments cover both internal dynamics well center mass diffusion beyond Rouse time. The key experimental results are (i) all chains equally mobile, (ii) basic segmental (Rouse) relaxation rate is unaffected even at highest concentrations, and (iii) apparently obstacles reduce significantly translational motion. This...

We propose a resolution to the puzzle presented by surface defects observed with STM at (111) facet of ${\mathrm{CeO}}_{2}$ single crystals. In seminal paper Esch et al. [Science 309, 752 (2005)] they were identified oxygen vacancies, but behavior these is inconsistent results density functional theory (DFT) studies vacancies in literature. resolve inconsistencies via DFT calculations properties both and fluorine impurities ${\mathrm{CeO}}_{2}(111)$, latter having recently been shown exist...

The excess free energy of small molecules in the amorphous polymers poly(ethylene) and poly(dimethylsiloxane) was calculated, using test-particle-insertion method. method applied to polymer configurations obtained from molecular dynamics simulations with differently prepared initial guess configurations. It found that calculated solubility coefficients strongly depend on quality configuration. Slow compression dilute systems, during which process only repulsive parts nonbonded Lennard-Jones...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAdhesive hard-sphere colloidal dispersions. A small-angle neutron-scattering study of stickiness and the structure factorC. G. De Kruif, P. W. Rouw, J. Briels, M. H. Duits, A. Vrij, R. MayCite this: Langmuir 1989, 5, 2, 422–428Publication Date (Print):March 1, 1989Publication History Published online1 May 2002Published inissue 1 March 1989https://pubs.acs.org/doi/10.1021/la00086a023https://doi.org/10.1021/la00086a023research-articleACS...