(746g) Protracted Colored Noise Dynamics in Molecular Dynamics Simulations of Block Copolymers

Block copolymers (BCPs) can phase separate to form periodic structures with small spacings, making BCPs an attractive option for furthering the ability of optical lithography to make dense arrays of features. Simulation of structural formation in these systems can help optimize the BCP system to produce small repeatable structures. Unfortunately, these BCP photoresist systems are highly viscous and the simulation of order formation requires very long simulation times. While coarse-grain and mean-field approaches have been applied to increase efficiency of these simulations, we apply a stochastic simulation to a coarse-grain model to further increase efficiency. This method, Protracted Colored-Noise Dynamics (PCND), adds colored-noise forces to increase local diffusivity while maintaining constant temperature with an integral energy controller. This method has been adapted to polymers by selectively applying the stochastic force to the polymer contour to artificially increase reptation to increase the efficiency of viscous polymer simulations. This work demonstrates the effects of PCND on a coarse-grained BCP system and explores the primary parameters involved in PCND. We show that PCND is able to increase the kinetics of defect annihilation in BCP systems more effectively than raising the temperature. It also avoids the unrealistic perturbation of polymer density and conformation that accompanies large temperature increases. PCND is shown to alter some properties of the BCP such as the pitch, yet once PCND is turned off the system returns to its natural state.