About building polymer models and equilibration

Hi !

Recently I am trying to calculate the elastic modulus of Teflon using Lammps. After building the model in Material Studio, I did geometry optimization and energy minimization in Material Studio. Then I transfer the .car file into the .data file.
Do I have to assign velocity to the atoms in the Lammps? Or do I have to balance and minimize again in the Lammps?
Below is my data file. thank you for your help!

Pittmann Schwabe
TEFLON.txt (3.8 KB)

Yes. That information is lost during creation of the data file (if it was ever there initially).

You will also have to equilibrate again, but if the transfer to the data file was done correctly, you won’t have to minimize again.

Thank you, Akohlmey!

I am not sure if I really understood your answer. My concept of getting the elastic modulus of Teflon is: → Using Material Studio to build an initial model and optimize the structure and minimize energy
→ Importing the model into Lammps
→ Moving atoms to imitat experiments in the real world
→ Calculating stress and strain to get the elastic modulus.
Where should I assign the Velocity of Atoms, if I use the data file that I posted on the top to do the simulation?
What’s more, could you tell me: whether every model has to be assigned velocity before the actual simulation?
Thank you!

Pittmann Schwabe

Since LAMMPS is a molecular dynamics code, I was assuming you want to do a molecular dynamics simulation.

To specifically compute the elastic modulus, you can follow the examples bundled with LAMMPS (for 0K look at examples/ELASTIC, for finite temperature look at examples/ELASTIC_T


Thank you. I will read the instruction carefully.