A previously developed method entitled “Protracted Colored Noise Dynamics” (PCND) was used to speed up the equilibration rate of dense viscous materials by several orders of magnitude. This method is compatible with any generic molecular mechanics force field, including atomistic or coarse-grained force fields. It adds non-random stochastic fluctuations (colored-noise) to typical molecular dynamics simulations to increase local diffusivity. The stochastic fluctuations are random force vectors on the atoms that decay exponentially with a characteristic time, and can vary in magnitude. The magnitude of these stochastic forces can be made large enough to significantly increase the system’s local diffusivity via a circumvention of the fluctuation-dissipation theorem. This circumvention of the fluctuation-dissipation theorem allows for arbitrarily large fluctuations without creating an over-damped system as a result of connection the between the variance in the stochastic fluctuation distribution and the system dissipation normally required by fluctuation dissipation. In contrast, we use an integral thermostat algorithm to manage the dissipation of the system. We have recently adapted PCND to linear polymer systems by constraining the stochastic fluctuation vectors to the backbone contour of the polymer chain. This enhances polymer chain reputation thereby increasing the local diffusivity. We have applied this to coarse-grained simulations of block copolymer photoresists to obtain four orders of magnitude speed up in the annealing of lamellar defects in these systems. We will discuss the optimal values of the width of the stochastic fluctuation distribution, and the associated relaxation time scale, as well as system perturbations to the system dynamics resulting from the application of this new method.<br/>

Protracted colored noise dynamics in polymer simulation

2019 Fall National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.