Our research work involves course grain Molecular Dynamics simulation of semicrystalline polyethylene. We have followed the paper by Belin et al. on “Modeling Method for Semicrystalline Polymers Controlling Aspects of the Morphology at the Molecular Scale for the Study of Mechanical and Physicochemical Properties” and are trying to replicate the simulation on semicrystalline polyethylene. In this paper, they have modeled and simulated semicrystalline polyethylene to find out its mechanical properties. Their semicrystalline PE before equilibration is shown in the figure a. The structure after equilibration is shown in figure b.
We have tried to replicate the modeling and simulation process and weren’t able to achieve a similar kind of structure. Our structure after simulation did not retain a well defined and uniform crystal structure.
Could you please let me know what changes could be made to achieve a uniform crystal structure?
figure [a]
I know the work of Belin quite well and I can advise you to go again through the full paper since it appears from your descriptions that you don’t quite get what is actually going on.
Figure a) here is actually an equilibrated PE configuration. Figure b) is a (highly!) strained structure. If you are referring to the b) subfigure of figure 12 of their paper, then you would also be incorrect since it is the same as subfigure a) you showed, but from a different angle.
The “well defined and uniform crystal structure” is also dependent on your simulation condition and model. This phrasing is also meaningless in the case of a semi-crystalline system since you are simulating an interface between amorphous and crystalline structures. Cristallinity has to be quantified through either local density measurement or local order parameter. A uniform periodic crystal is very easy and straightforward to build with standard tools or even a simple script with the cell parameters of PE. You can look into the work of the Rutledge group or previous work from Rousseau and Pandiyan.
The connection and equilibration algorithms are explained in great details in the paper and partly done in the MedeA Builder based on Theodorou and Suter’s work. So if you wand to reproduce their result you should either get in touch with the people from MedeA or write your own connecting algorithm (something that requires a bit of work but is totally feasible). Without more information on your simulation procedure, it is impossible to guide you more than that,
