A Monte Carlo simulation study has been conducted to assess the ability of recently proposed force fields predict orthobaric densities, second virial coefficients, and P-V-T data for short long alkanes. new, modified field is that provides good agreement with experimental phase equilibrium coefficient over wide ranges temperature chain length.

A novel formalism is presented for simulation of polymers in expanded grand canonical and Gibbs ensembles. Molecular creation destruction attempts are replaced by transition between states a tagged chain variable length. Results simulations hard-core fluids the bulk slit pore ensemble vapor–liquid equilibria square-well chains.

Ordered intermetallic nanoparticles are promising electrocatalysts with enhanced activity and durability for the oxygen-reduction reaction (ORR) in proton-exchange membrane fuel cells (PEMFCs). The ordered phase is generally identified based on existence of superlattice ordering peaks powder X-ray diffraction (PXRD). However, after employing a widely used postsynthesis annealing treatment, we have found that claims "ordered" catalysts were possibly/likely mixed phases intermetallics...

Recently, Zhao et al. [Proc. Natl. Acad. Sci. U. S. A., 2011, 108, 2684] reported the phase behavior of monolayers polymeric Brownian squares platelets. As density is increased, this system exhibits formation two crystal structures not expected for particles with square symmetry, namely, a hexagonal rotator and rhombic phase. Molecular simulations by Wojciechowski Frenkel [Comp. Met. Technol., 2004 10, 235] had predicted instead tetratic phases. In work, we report Monte Carlo simulation...

Although extensive efforts have been devoted to understanding electronic transport in conjugated polymers, little is known about their ionic conduction characteristics relation polymer chemistry, processing, and morphology. This work presents a combined computational experimental study on morphology ion thin-film blends of polythiophene derivatives bearing oligoethylene glycol side-chains lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). Using molecular dynamics (MD) simulation, we show...

The continuum configurational bias (CCB) Monte Carlo method has been extended to perform elementary moves that involve the rearrangement of inner segments flexible chains. When regrowing sites, continuity with rest chain is ensured by disregarding those configurations would imply an unrealistic elongation bonds once reconstructed. formalism presented here also allows simulation branched chains and crosslinked-network structures. proposed in this work are used conjunction alternative...

The phase behavior of suspensions colloidal hard tetragonal parallelepipeds ("TPs") (also known as rectangular nanorods or nanobars) was studied by using Monte Carlo simulations to gain a detailed understanding the effect flat-faceted particles on inducing regular local packing and long range structural order. A TP particle has orthogonal sides with lengths a, b, c, such that a=b its aspect ratio is r=c/a. diagram for perfect TPs mapped out ratios ranging from 0.125 5.0. Equation state...

The last decade has seen a rapid growth in the number of simulation methods and applications dealing with sampling transition pathways rare nanoscale events. Such studies are crucial, for example, understanding mechanism kinetics conformational transitions enzymatic events associated function biomolecules. In this review, broad account path approaches is provided, starting from general concepts, progressing to specific principles that underlie some most important methods, eventually singling...

The goal of this work is to study via molecular simulations the wetting kinetics a rough surface by an oily fluid. We use forward flux sampling compute transition rate and elucidate mechanism small droplet on nails. nails provide re-entrant geometry necessary keep in nonwetted, composite state. effects nail height, size, chemistry are investigated. Because must touch bottom transition, increasing height effective way increase barrier for both phobic slightly philic drops, although as fluid...

Watching growth, step by Polymers can grow through the stepwise addition of monomers to an active end site. One might think that this would happen in a continuous linear process. With focus on ring-opening metathesis polymerization norbornene catalyzed Grubbs' catalyst, Liu et al. describe growth single polymer chain. By attaching one growing bead exerting constant force it, they measured extension occurring during polymer. Oddly, did not increase continuously. Instead, it exhibited...

Molecularly doped conjugated polymers with polar side chains are an emerging class of conducting materials exhibiting enhanced and thermally stable conductivity. Here, we study the electronic conductivity (σ) corresponding thermal stability two polythiophene derivatives comprising oligoethylene glycol chains: one having oxygen attached to thiophene ring (poly(3-(methoxyethoxyethoxy)thiophene) (P3MEET)) other a methylene spacer between (poly(3-(methoxyethoxyethoxymethyl)thiophene) (P3MEEMT))....

A new method is proposed for calculation of the chemical potential macromolecules by computer simulation. Simulations are performed in an expanded ensemble whose states defined length a tagged molecule variable size. configurational-bias sampling and preweighting scheme introduced to facilitate transitions between such states. The usefulness illustrated calculations hard chain molecules over wide range densities. here shown offer significant advantages other available methods potentials,...

This review provides a discussion of recent techniques for simulation phase equilibria complex fluids. Monte Carlo methods are emphasized over molecular dynamics methods. We describe developments, such as the use expanded-ensemble, tempering, or histogram reweighting techniques. Our developments is aimed at general audience and intended to provide an overview main advantages limitations each particular technique. References provided allow interested readers identify trace back most...

A new approach is developed for identifying suitable reaction coordinates to describe the progression of rare events in complex systems. The method based on forward flux sampling (FFS) technique and standard least-square estimation (LSE) it denoted as FFS-LSE. FFS algorithm generates trajectories transition between stable states chains partially connected paths, which can then be used obtain “on-the-fly” estimates committor probability final region, pB. These pB data are screen a set...

Particle-based molecular simulations of pure diblock copolymer (DBC) systems were performed in continuum space via dissipative particle dynamics and Monte Carlo methods for a bead-spring chain model. This model consisted chains soft repulsive particles often used with dynamics. The gyroid phase was successfully simulated DBC melts at selected conditions provided that the simulation box size commensurate lattice spacing. Simulations concentrated where is expected to be stable which allowed us...

In this work, we present an adaptive algorithm to optimize the phase space sampling for simulations of rare events in complex systems via forward flux (FFS) schemes. FFS, interfaces are used partition along order parameter λ connecting initial and final regions interest. Since kinetic “bottleneck” not usually known beforehand, procedure is that first finds these by estimating rate constants associated with reaching subsequent interfaces; thereafter, FFS simulation reset concentrate on those...

We consider an atomistic model to investigate the flux of water through thin Linde type A (LTA) zeolite membranes with differing surface chemistries. Using molecular dynamics, we have studied flow under hydrostatic pressure a fully hydrated LTA film (~2.5 nm thick) capped hydrophilic and hydrophobic moieties. Pressure drops in 50-400 MPa range were applied across membrane, was monitored for at least 15 ns simulation time. For membranes, molecules adsorb surface, creating highly structured...

The simulation of homogeneous liquid to vapor nucleation is investigated using three rare-event algorithms, boxed molecular dynamics, hybrid umbrella sampling Monte Carlo, and forward flux sampling. Using novel implementations these methods for efficient use in the isothermal-isobaric ensemble, free energy barrier kinetic rate are obtained a Lennard-Jones fluid at stretched superheated conditions. From surface mapped as function two order parameters, global density largest bubble volume, we...

When in contact with a rough solid surface, fluids low surface tension, such as oils and alkanes, have their lowest free energy the fully wetted state. For applications where nonwetting by these phillic is desired, some barrier must be introduced to maintain nonwetted composite One way create this free-energy fabricate roughness reentrant geometry, but question remains whether sufficiently high prevent wetting. Our goal quantify landscape for wetting transition of an oily fluid on nails...

We perform molecular dynamics simulations on a bead-spring model of pure polymer grafted nanoparticles (PGNs) and blend PGNs with melt to investigate the correlation between PGN design parameters (such as particle core concentration, grafting density, length) properties, such microstructure, mobility, viscous response. Constant strain-rate were carried out calculate viscosities constant-stress ensemble was used yield stresses. The systems are found have less structural order, lower...

This work reveals the structure and sequence effects on ion electron conductivity. Increased oxygen content leads to increased ionic reduced electronic conductivity, backbone distance increases both conductivities.

Abstract Organic semiconductors based on liquid crystal (LC) molecules have attracted increasing interest. In this work, two linear LCs 2,5‐bis(thien‐2‐yl)thieno[3,2‐b]thiophene (BTTT) mesogen are designed and synthesized, including BTTT/dEO3 with symmetrically attached tri(ethylene oxide) groups BTTT/mEO6 one asymmetrically hexa(ethylene group. These comparable functional‐group compositions but different molecular geometries, leading to their moderately material performances. Both show...