Protracted Colored Noise Dynamics Applied to Nanoscale Studies of Block Copolymers

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Nicoloso, Daniel L.
Henderson, Clifford
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Coarse-grained molecular dynamics is an accurate and versatile tool for understanding the dynamic behavior of molecules at a wide variety of length and time scales. This especially useful for understanding the kinetics of self-assembly processes in block copolymers, as these systems are difficult and expensive to study experimentally. One of the current limitations of molecular dynamics simulations is that when molecules in the system must overcome a large activation energy barrier, the computing speed decreases by several orders of magnitude. Protracted colored noise dynamics is a variation of molecular dynamics, which was developed to address the issue by incorporating stochastic colored noise into force calculations in simulation. Hypothetically, this should improve phase space sampling efficiency in molecular dynamics simulations and force kinetically inhibited systems to an equilibrium state more quickly. The purpose of this study was to apply protracted colored noise dynamics to simulations of block copolymers, including systems with kinetic limitations. The first goal of this study was to investigate potential computational speed up due to overcoming kinetic limitations with protracted colored noise dynamics. The results were very promising, showing an order of magnitude reduction in computational time for high activation energy simulations. The second goal was investigate the effect of random forces on the equilibrium structure of block copolymers in simulation. The results show that for sufficiently strong random forces, the block copolymers are highly disordered at equilibrium. In the course of this study, a threshold parameter space for protracted colored noise dynamics was developed to understand the limitations on noise strength.
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