LJ and Buckingham potential

Hello Everyone,

Is there any way to use LJ and Buckingham potential for one pair interactions at different cut off in LAMMPS. I want to use Buckingham for cutoff distance up to rmin, rc=rmin, and for the cutoff bigger than rmin, rc> rmin (for the same pair atoms) I want to use LJ potential. I looked at the hybrid/overlay style but it seems that I can not use it for the purpose that I want.

I appreciate your comments.

Best,

Leila

Perhaps you should think again about why such a feature is not available in Lammps…

How are you stitching your overall curve at the rmin? Force discontinuities rings a bell?..

But there is always a bullet for the Russian roullet player:

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

Carlos

Carlos,

Thank you for the link.

Actually, I converted the LJ parameters to the Exp-6 parameters and both have the same well depth and location (minimum) but the problem that I still have, I asked question about this before, is that when I use the LJ parameters I see the energy transfer from the excited molecule to the bath gas but when I use the Exp-6 parameters (LJ converted to the Exp-6 parameters) I don’t see energy transfer unless I decrease the cutoff distance to the rmin of the potential !!!

  • I keep trying to check everything and now I want to see if I use the Buckingham at rmin and LJ at longer range or opposite what I see.

Best,

Leila

I see that rmin is actually the location of your minimum indeed (read a bit too fast your earlier email) thus no worries about force discontinuities then. You can then go ahead and tabulate your glued potential. I do remember your past problem which sounded a bit weird about a molecule not being able to transfer kinetic energy to others or something like that…

Carlos

Carlos,

Thank you.

Best,

Leila

You can tabulate the values and use pair_style table.

Steve

Steve,

Thank you.

Best,
Leila