High potential energy in modeling graphene sheets

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1

Hi Lammps users,

I am modelling five graphene layers. In this model, I have fixed the carbon atoms by using zero velocity and fix freeze all setforce 0 0 0 because I want a rigid surface. However, I am getting very high positive potential energy (e14). The potential energy will decrease if zero velocity and fix freeze are removed. But, the graphite is not rigid anymore, and it contains some wrinkles in it. I also changed the force field to Tersoff and I have the same results.
Has anyone had such a problem before?

Thanks,
Atefeh

2

Sounds like you have a bad initial geometry that.

Axel.

3

Hi Axel,

Thanks so much for your email.
Yes, I also think the problem is the initial geometry. How can I solve this problem?
Now, I am using VMD for creating the initial structure.

Thanks,
Atefeh

4

Hi Axel,

Thanks so much for your email.
Yes, I also think the problem is the initial geometry. How can I solve this problem?

it don’t have a crystal ball, so i cannot know what you are doing and where things are going wrong.
you need to visualize the input, also taking into account box size and boundary conditions.

perhaps if you compute and output the per-atom energy and output it with a custom dump, you can identify which atoms have very high-potential energy.

Now, I am using VMD for creating the initial structure.

please note that VMD uses empirical parameters to build structures, they may not be optimal for your specific potential parameters.
also VMD does not pay much attention to box geometry (most visualization and analysis is not aware of periodic boundaries or box sizes for that matter).

axel.