compute lj pair energy

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1

Hi Dear

I have 9 atom types in my system. I want to calculate LJ pair energy between 17 and 89 atom types, but I dont find the command in LAMMPS to do it.

Please guide me.

2

Two ways to do this:

1)
Take a look at "compute group/group"
http://lammps.sandia.gov/doc/compute_group_group.html

2)
If you have already run the simulation, you can recalculate the
pair-energy using the "rerun" command (throwing away interactions you
don't care about).

http://lammps.sandia.gov/doc/rerun.html

When you do this, you can use "pair_coeff" commands to turn off all
interactions between atoms between the wrong pairs of atoms. For
example, something like:

pair_style hybrid lj/cut 2.5 YOUR_PAIR_STYLE
pair_coeff * * lj/cut 0 0
pair_coeff 1*7 8*9 YOUR_PAIR_STYLE PARAMS...
rerun dump.file dump x y z

(I hope I got this correct. This way, the remaining pair energy of
the system will contain only the interactions you care about, between
atoms 1*7 and 8*9, in this case.)

You can also use "rerun" together with "compute group/group" as well.
Cheers

Andrew