Non-equilibrium Molecular Dynamics Simulations of Coarse-Grained Polymer Systems

Non-equilibrium Molecular Dynamics Simulations of Coarse-Grained Polymer Systems 

The rigorous solution of the time-dependent, quantum-mechanical, many-body problem is numerically unfeasible. The problem thus must be reduced to classical mechanics and coarse-grained models have to be introduced. In particular for NEMD simulations, the modeling of solvent effects can be crucial and the complexity of the problem is highly dependent on whether the external stimuli are strong or weak and whether they are constant in time or nonstationary. 

When hydrodynamic effects are not expected to be important, it is often convenient to simulate without explicit solvent molecules. This approach can stUl be justified even when hydrodynamic flow becomes relevant, but solvent-related degrees of freedom have to be incorporated on a certain coarse-grained level. To reproduce hydrodynamic effects in the continuum limit, mesoscale hydrodynamic techniques 

Owing to its simplicity, the Langevin (LGV) thermostat is one of the most applied methods to perform simulations in the canonical ensemble. In this approach, the simulated particles are coupled to an external heat bath at constant temperature. The dissipative force acting on particle i is proportional to its velocity  

Galilean invariance is lost due to the coupling of monomers to the heat bath, which mimics a solvent that rests in the laboratory frame. Therefore, the method belongs to the class of profile-biased thermostats [138]. This can be demonstrated easily Let us consider a film of linear polymers confined by two adsorbing substrates. Shear is applied by moving the upper substrate with a constant velocity, w, while the lower 

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