We present an extensive molecular-dynamics simulation for a bead spring model of melt linear polymers. The number monomers N covers the range from N=5 to N=400. Since entanglement length Ne is found be approximately 35, our chains cover crossover nonentangled entangled regime. Rouse provides excellent description short N<Ne, while dynamics long can described by reptation model. By mapping onto chemical species we give estimates times and distances onset slowing down in motion due...

We describe an efficient and general algorithm for simulating polymers, which can be used single, large chains as well many-chain systems. It allows us to distinguish solvent effects from interchain on the dynamics of chains. The method is tested linear cyclic 50 200 monomers. have confirmed two theoretical results not been observed numerically or experimentally, namely anomalous behavior S(q) rings ${t}^{0.54}$ power law motion a monomer in self-avoiding chain undergoing Rouse relaxation.

The free-volume model, which has been useful for describing the behavior of viscosity $\ensuremath{\eta}$ dense liquids and glasses, is extended to account their thermodynamic as well. Experimental results heat capacity ${C}_{p}$ volume $\overline{v}$ show that system falls out complete, metastable equilibrium at glass transition temperature ${T}_{g}$. As a first step in understanding these universal phenomena, theory underlying phase, amorphous developed. Recent molecular-dynamic...

We have performed a systematic, large-scale simulation study of granular media in two and three dimensions, investigating the rheology cohesionless particles inclined plane geometries, i.e., chute flows. find that over wide range parameter space interaction coefficients inclination angles, steady-state flow regime exists which energy input from gravity balances dissipated friction inelastic collisions. In this regime, bulk packing fraction (away top free surface bottom plate boundary)...

The viscoelastic properties of high molecular weight polymeric liquids are dominated by topological constraints on a scale. In manner similar to that entangled ropes, polymer chains can slide past but not through each other. Tube models dynamics and rheology based the idea entanglements confine chain small fluctuations around primitive path follows coarse-grained contour. Here we provide microscopic foundation for these highly successful phenomenological models. We analyze state in terms...

The phase diagram and dynamical properties of systems particles interacting through a repulsive screened Coulomb (Yukawa) potential have been calculated using molecular lattice dynamics techniques. contains both melting transition from fcc to bcc crystalline phases. These transitions studied as function shape (screening length) compared phenomenological criteria for temperatures such those Lindemann Hansen Verlet. with increasing temperature is shown result higher entropy in the because its...

Several methods for preparing well equilibrated melts of long chains polymers are studied. We show that the standard method in which one starts with an ensemble correct end-to-end distance arranged randomly simulation cell and introduces excluded volume rapidly, leads to deformation on short length scales. This is strongest relaxes only after have moved their own size. Two shown overcome this local chains. One first pre-pack Gaussian chains, reduces density fluctuations system, followed by a...

We describe molecular dynamics simulations of fluid films confined between two solid walls. The consist spherical molecules, or flexible linear chains with up to twenty monomers. When the wall separation is only a few diameters, crystalline glassy order induced across film. onset phase characterized by rapidly increasing relaxation times. These manifest themselves through changes in diffusion constant and response shear. viscosity exhibits same power-law scaling shear rate that was observed...

Abstract Computer modelling has been carried out to study normal grain growth in three dimensions. The approach consists of digitizing the microstructure by dividing polycrystalline material into small volume elements and storing spatial location crystallographic orientation each element. An energy is assigned between element its neighbours, such that neighbours having unlike orientations provide weaker bonding than like orientations. annealing treatment during which occurs simulated using a...

Molecular dynamics simulations were conducted to investigate the structural properties of melts nonconcatenated ring polymers and compared linear polymers. The longest rings composed N=1600 monomers per chain which corresponds roughly 57 entanglement lengths for comparable For rings, radius gyration squared was found scale as N 4/5 power an intermediate regime 2/3 larger indicating overall conformation a crumpled globule. However, almost all beads are "surface beads" interacting with other...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTStructure of a grafted polymer brush: molecular dynamics simulationMichael Murat and Gary S. GrestCite this: Macromolecules 1989, 22, 10, 4054–4059Publication Date (Print):October 1, 1989Publication History Published online1 May 2002Published inissue 1 October 1989https://pubs.acs.org/doi/10.1021/ma00200a041https://doi.org/10.1021/ma00200a041research-articleACS PublicationsRequest reuse permissionsArticle Views2738Altmetric-Citations310LEARN ABOUT...

Pebble-bed nuclear reactor technology, which is currently being revived around the world, raises fundamental questions about dense granular flow in silos. A typical core composed of graphite fuel pebbles, drain very slowly a continuous refueling process. Pebble poorly understood and not easily accessible to experiments, yet it has major impact on physics. To address this problem, we perform full-scale, discrete-element simulations realistic geometries, with up 440,000 frictional,...

Density functional theory (DFT) molecular dynamics (MD) and classical MD simulations of the principal shock Hugoniot are presented for two hydrocarbon polymers, polyethylene (PE) poly(4-methyl-1-pentene) (PMP). DFT results in excellent agreement with experimental data, which is currently available up to 80 GPa. Further, we predict PE PMP Hugoniots 350 200 GPa, respectively. For comparison, studied reactive nonreactive interaction potentials. latter, exp-6 Borodin et al. showed much better...

Molecular dynamics simulations were conducted to investigate the dynamic properties of melts nonconcatenated ring polymers and compared linear polymers. The longest rings composed N = 1600 monomers per chain which corresponds roughly 57 entanglement lengths for comparable found diffuse faster than their counterparts, with both architectures approximately obeying a D ∼ N(-2.4) scaling law large N. mean-square displacement center-of-mass follows sub-diffusive behavior times distances beyond...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTStructure of grafted polymeric brushes in solvents varying quality: a molecular dynamics studyGary S. Grest and Michael MuratCite this: Macromolecules 1993, 26, 12, 3108–3117Publication Date (Print):June 1, 1993Publication History Published online1 May 2002Published inissue 1 June 1993https://doi.org/10.1021/ma00064a019RIGHTS & PERMISSIONSArticle Views1435Altmetric-Citations310LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum...

The properties of dendrimers ("starburst" molecules) under varying solvent conditions are studied using molecular dynamics simulations. found to have a compact (space filling) structure all conditions, with radius gyration which scales the number monomers as RG ∝ N1/3. For high generation dendrimers, there is distinct region constant monomer density. density in this depends only on quality and independent number. When contributions different generations overall profile separated, we find...

We study static packings of frictionless and frictional spheres in three dimensions, obtained via molecular dynamics simulations, which we vary particle hardness, friction coefficient, coefficient restitution. Although hard-spheres are always isostatic (with six contacts) regardless construction history restitution achieve a multitude hyperstatic that depend on system parameters history. Instead immediately dropping to four, the coordination number reduces smoothly from $z=6$ as $\mu$...

We present an experimental study of the frequency \ensuremath{\omega} dependence and volume fraction \ensuremath{\varphi} complex shear modulus ${G}^{*}(\ensuremath{\omega},\ensuremath{\varphi})$ monodisperse emulsions which have been concentrated by osmotic pressure \ensuremath{\Pi}. At a given \ensuremath{\varphi}, elastic storage ${G}^{\ensuremath{'}}(\ensuremath{\omega})=\mathrm{Re}[{G}^{*}(\ensuremath{\omega})]$ exhibits low-frequency plateau ${G}_{p}^{\ensuremath{'}},$ dominating...

Molecular-dynamics simulations of noncohesive granular assemblies under shear are described. At low rate \ensuremath{\gamma}\ifmmode \dot{}\else \.{}\fi{}, the assembly is unstable to uniform motion and exhibits stick-slip dynamics involving periodic dilatancy transitions gravitational compactification. Steady-state occurs at larger \.{}\fi{} where 6--12 layers grains flow over a compact, static assembly. A phase boundary, characterized by discontinuity in an enhanced normal stress,...