Mixing atoms and coarse-grained beads in modelling polymer melts

We present a hybrid coarse-grained-atomistic model for soft materials that enables an easy and smooth on-the-fly change of the number of degrees of freedom considered during the simulation. The model employs the coarse-grained force fields developed using the Iterative Boltzmann Inversion and classical atomistic force fields. The resolution of the model can be automatically controlled by the software and there is no need of any type of interface when switching on or off the degrees of freedom. The model is used on melt of atactic polystyrene showing that the soft coarse-grained potential merges extremely well with the atomistic force field. The model is able to reproduce correctly all the global and local structural properties at any level of resolution. The method has been implemented in our simulation code IBIsCO and can be readily used to simulate any kind of material interface allowing a proper multiscale approach to material science.