[lammps-users] fix deform problem

Dear friends,

Does not any one here have any ideas about the problem I am facing with?

As I put CNT under tension with a constant rate e.g.(erate=0.2), the nanotube extends about 30% and after that it’s length does not change anymore. The same thing happens for (erate=0.1), but the nanotube extends only about 5% and keeps that lenght in spite of box extension.

When I checked the box size, I saw that the box size is changing as it should. I am using “fix deform” command and it is said that the atoms inside the box move proportionally to the box size.
I want to ask to know why the atoms do not follow the box extension after a while?

Best
Mehrdad

If you are using bond order potential, where bonds can break, what you are seeing is expected. After certain points, the bond will break across of the interface and then CNT will just relax itself to its equilibrium value (if your system is periodic in that direction)

I am using AIREBO potential function. But I am modeling the same nanotube with the same potential function. When I change strain rate (erate) in fix deform command, the stop point changes and that seems so strange. for erate=0.2 it extends up to 30% while for erate=0.1 it just extends about 5%. I want to know the relationship between strain rate and extension (which should not be exist at all)

Thanks for your help
Mehrdad