[lammps-users] CNT modeling Question

Hi Friends
Thanks for your explanations. I have some questions about what you have explained:
A) I tried the first method (energy minimization) and have some problems.
1- I have defined my CNT in a read_data file. Now, I can not change the box size by using “fix_deforme” or “displace_box”.
Would you please help me how to solve it?
2- How should I calculate Young modulus of CNT in this way? Is it the same as done in Aidan’s work?
3- As I modeled my CNT with “constant engineering strain rate” using “fix deform” command, I saw that CNT have a periodic
movement. It starts to expand at first, but after a while it shrinks. Based on the fact that I have put a constant positive strain
rate or a positive displacement in displace_box command, how can I explain it? (I have experienced the same happening while
I only used “fix addforce” command)

B)Trying the second method (fix npt, fix deform), I faced with theses problems,
1-There is a huge fluctuation in my CNT which seems strange.
2-The same periodic movement happened (as I explained in previous part), but after first contraction the system has a very
slow expansion with considerable fluctuatuion.
3-How should I calculate oung modulus in this method? Is it the same as in energy minimization method?
4-Is there any need to add tension to CNT by using “addforce” command?

Best regards
Mehrdad

Hi Friends
Thanks for your explanations. I have some questions about what you have
explained:
A) I tried the first method (energy minimization) and have some problems.
1- I have defined my CNT in a read_data file. Now, I can not change the
box size by using "fix_deforme" or "displace_box".
Would you please help me how to solve it?

yes you can - what happens when you try?

Steve

But I have some problems. When I use "fix_deforme" command with
"erate" of 0.1 , I expect to see 100% deformation after a 10
picoseconds based on LAMMPS manual. But it does not work well and I
just see a little movement and a great fluctuation.

Regards