Movement of atom layer

Hi, LAMMPS users

I have a question about fixing the initial position of atoms. I’m calculating the velocity autocorrelation of graphene on Cu with different distance between two materials. When I set 40angstrom for the distance and ran LAMMPS. Graphene layer moved to the Cu surface while calculating. In order word, graphene layer was at the initial position but it closed the Cu when the calculation started as attached files. How can I fix graphene layer above Cu surface with 40angstrong distance?

Here is my input script. I’d really appreciate it if you give me comments.

Thanks,

Jaeyoung

This is the control script for LAMMPS

echo both

inintial.png

calculating.png

You could use fix spring to restrain the center of mass distance between the two groups of atoms.

Axel

Hi,

Thank you for your comments.

I used “fix spring/self” to restrain the center of mass distance between the two groups.

As below my scripts, I checked “fix spring/self” before calculation of VACF and it worked.

Two groups had the initial position. After that, I added the calculation part of VACF, two groups close to each other. They did not keep initial position while calculating VACF.

If you tell me what’s wrong, I’d really appreciate it.

Thanks,

Jaeyoung Jeong