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I have a bead-spring model of a polymer melt and I would like to simulate what happens when a solvent is added to the system.

The most direct way to do this would be to add solvent particles into the system. But my simulations already take enough time so I would like to avoid this approach.

I think the best approach would be to change the interaction energies of the system. However, I'm not sure how I should change the interaction parameters to correctly represent the presence of a solvent.

Is this the correct approach? How can I determine appropriate parameters to mimic my solvent?

My system uses a 6-12 LJ potential and a FENE bonding potential.

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I assume you are currently running a deterministic simulation which explicitly computes the time evolution of all degrees of freedom using Newton's equations. In order to implicitly simulate a solvent, what you want instead is a simulation that computes the time evolution of only a subset of relevant degrees of freedom (i.e. those of your polymers). It turns out that the evolution of this subset can be described using the stochastic Langevin equation. Instead of explicitly simulating solvent particles, it applies noise to your polymers that mimics random collisions with solvent particles.

For a very detailed description of why this is the case, see section 2 of Roux et al..

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  • $\begingroup$ This is a valid approach, but there won't be hydrodynamic interaction between the monomers if you simply use Langevin dynamics, so this methods is only valid if the hydrodynamic interaction between the monomers can be neglected (high density). $\endgroup$ – valerio Jan 10 '18 at 23:05

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