Dear Sir,
To calculate the elastic constant of polymer composite, a constant strain minimization method I want to use.
can we apply this method in LAMMPS ?
This method is applied on the example script ELASTIC (in the installation folder of LAMMPS). Although you have to equilibrate your structure very well and also be sure that the minimization algorithm has converged correctly. It is very difficult to implement those things on polymers (especially epoxies). Please let me know for your results!
This is actually how the born/matrix implements the computation from Zhen et al. Note however that the difference in instantaneous stress only gives the born term of the elastic constants. For a computation of the full elastic constant, you have to compute the difference using the finite temperature stress computed in NVT.
As @Iakovos_Delasoudas puts it, it is complicated to get meaningful results with polymers. You should consult the related literature. These issues have been extensively discussed.
Thanks Sir
Thank you, Sir
Respected Sir,
As you suggested, I used ELASTIC example script for my simulation box [Nafion + water molecules], but I am not getting good results.
In LAMMPS examples, ELASTIC_T directory include - Born_matric and Deformation examples.
Colud you please suggest which one is more relevant for polymer system [Nafion + water molecules].
Thanks and Regards
Sachin Kumar Varshney
Hello!
As I mentioned earlier the ELASTIC script uses the force aproximation molecular mechanics Methode originally introduced by Theodorou & Sutter.
The most key points you have to be careful are
- Have a lot of configurations to have good statistics
- Minimize the structures properly cause the results depend rally much on that.
Iām any case if you want to compute the elastic properties of a polymer system I suggest just deforming the structure using fix deform and then measure the slope of the stress strain curve!
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Thanks Sir