Directed Bridging Methods for Fast Atomistic Monte Carlo Simulations of Bulk Polymers

527

737

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 of chains with the correct end-to-end distance arranged randomly in the simulation cell and introduces the excluded volume rapidly, leads to deformation on short length scales. This deformation is strongest for long chains and relaxes only after the chains have moved their own size. Two methods are shown to overcome this local deformation of the chains. One method is to first pre-pack the Gaussian chains, which reduces the density fluctuations in the system, followed by a gradual introduction of the excluded volume. The second method is a double-pivot algorithm in which new bonds are formed across a pair of chains, creating two new chains each substantially different from the original. We demonstrate the effectiveness of these methods for a linear bead spring polymer model with both zero and nonzero bending stiffness, however the methods are applicable to more complex architectures such as branched and star polymer.

Section: Double-pivot-md Hybrid Algorithmmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Equilibration of long chain polymer melts in computer simulations

Auhl

Everaers

Grest

et al. 2003

527

737

“…A variety of different particle movement schemes have been used, including simple methods moving individual particles 15 and evolving the system with torsional rotations of bonds in polymers. [16][17][18] So-called bridging moves have also been introduced to handle branching polymers, 19,20 and more recently "event-chain" algorithms have been introduced to handle hard sphere particles. 21,22 An important bridge between the MC methods above and our hydrodynamically coupled method below lies in the work of Maggs.…”

Section: Introductionmentioning

confidence: 99%

Wavelet Monte Carlo dynamics: A new algorithm for simulating the hydrodynamics of interacting Brownian particles

Dyer

Ball

2017

We develop a new algorithm for the Brownian dynamics of soft matter systems that evolves time by spatially correlated Monte Carlo moves. The algorithm uses vector wavelets as its basic moves and produces hydrodynamics in the low Reynolds number regime propagated according to the Oseen tensor. When small moves are removed, the correlations closely approximate the Rotne-Prager tensor, itself widely used to correct for deficiencies in Oseen. We also include plane wave moves to provide the longest range correlations, which we detail for both infinite and periodic systems. The computational cost of the algorithm scales competitively with the number of particles simulated, N, scaling as N ln N in homogeneous systems and as N in dilute systems. In comparisons to established lattice Boltzmann and Brownian dynamics algorithms, the wavelet method was found to be only a factor of order 1 times more expensive than the cheaper lattice Boltzmann algorithm in marginally semidilute simulations, while it is significantly faster than both algorithms at large N in dilute simulations. We also validate the algorithm by checking that it reproduces the correct dynamics and equilibrium properties of simple single polymer systems, as well as verifying the effect of periodicity on the mobility tensor.

“…To overcome these limitations, Theodorou and coworkers have proposed connectivity altering MC moves [1][2][3][4][5][6][7] that improve the relaxation of long-range modes, namely the end-to-end autocorrelation function. In one such move, the connectivity of inner segments of a molecule is exchanged between two polymer chains, thereby resulting in a drastic change in the end-to-end vector in a single move.…”

Section: Introductionmentioning

confidence: 99%

A new double-rebridging technique for linear polyethylene

Banaszak¹,

Pablo²

2003

A variable connectivity, double-rebridging Monte Carlo ͑MC͒ technique is developed for simulation of long chain molecules. The method changes the connectivity of inner segments of two chain molecules by making use of a recently proposed inner-chain rebridging scheme ͓Chen et al., J. Chem. Phys. 113, 11382 ͑2000͔͒. The new method yields results consistent with other molecular dynamics and MC methods, but it enhances considerably the rate of equilibration of chain end-to-end vectors for long molecules. The new method is tested for linear polyethylene melts at 600 K. Polyethylene is modeled as linear 200 and 1000 carbon chains, respectively, using the NERD united-atom force-field ͑Nath, Escobedo, and de Pablo revised united-atom force field͒ ͓Nath et al.,