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[lammps-users] Question about Pair Coeff for Beads of same atoms types
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[lammps-users] Question about Pair Coeff for Beads of same atoms types


From: George Ray <uraykol12@...24...>
Date: Fri, 23 Jun 2017 16:07:22 -0400

Hello everyone,

I am using Lammps 14May-2016 version. I will describe my system first before asking my question. Basically it is a bead spring model. I have 4 beads to make up one chain. And there are many chains arranged together in a bundle. All the beads are of the same atom type and have the same mass.

Besides the harmonic bond style, angle style and dihedral styles, there are lj 6-12 potential fit between each beads in a chain and a lj 9-6 potential between beads in the adjacent chains.

Now my question is by specifying a command like "pair_coeff 1 1 100.0 3.5 9.0" , I can specify the interactions between beads in each of the chains. However what do I do for capturing the lj 9/6 potential which is basically between chains?

I thought of one solution. I can change the atom types in each chain and modify the data file. For example, if there are 8 chains I can have atom types 1-8. The lj9/6 can be captured by using something like the "pair_coeff 1 2 100.0 3.5 9.0" and so on. However, the problem is if I have many chains (around 50), it is very tedious to capture each cross term pair_Coeff command.  Is there a better way for this? Any feedback will be much appreciated.

Thank you so much for your help.

Regards,