I am using AIREBO potential with a cutoff distance of 2.0 A to find the stress-strain behaviour of a pristine graphene using LAMMPS. The stress-strain plot follows the experimental stress-strain plot almost exactly till the failure point but then inexplicable shows a hardening behaviour. I am using periodic boundary conditions in both x and y directions and applying uni-axial stress in the zigzag direction.
The relevant input lines are:
pair_style airebo 2.0
pair_coeff * * CH.airebo C
neighbor 2.0 bin
neigh_modify delay 10 check yes
I have attached the stress-strain plot which I obtained using the pxx command.
Dear Abhilash
The scale factor (last parameter in pair style command) has been chosen wrong. In this style 2.0 is scale factor for Sigma C-C (or any sigma you may need). According to CH.airebo complemented in lammms potential files, scale factor multiplied by 3.4 (Sigma C-C) which produces cutoff of 10.2 Angstrom. You may change the scale factor to 0.588 that would only applied to Lennard-Jones part of potential. Then the best choice must be modification of airebo potential file.
Dear Abhilash,
Could you please hear if you improved your problems about stress-strain behavior?
I have a similar problem in ultimate strain value is about 0.4 while in other papers I found it from 0.13 to 0.25!
How can I resolve this issue?
Regards
Amir
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