[lammps-users] CNT simulation

Many thanks for your help.
Is it possible to use a combination of fix and run commands inside an “if” command after “then” or “else”?

Best
Mehrdad

You can use multiple commands as part of the "then"
or "else" syntax. The if command doc page explains
how to do this.

Steve

Thanks for replies.
I have a question. 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

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?

This is now a long thread. But if you use fix deform with the remap none option
(discussed earlier), then the CNT atoms should not move with the
deformation. They
may move due to other forces. If you don't want them to move at all, then
don't time integrate them (and use remap none).

Steve

Thanks a lot Steve.This problem has solved. But I faced a new problem and have announced it in group. I will be happy to hear your answer.
Thanks again,
Mehrdad

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

Does the CNT act on itself? I.e. you have defined a pair
potential between CNT atoms, AIREBO or the like? Just b/c
you stretch the box, doesn't mean the atoms will move with
it indefinitely if the CNT is like a rubber band that will tend
to snap back to close to its original length.

Steve