Dear LAMMPS users
I am trying to use Morse potential along with long range coulombic term Z1Z2/r^2 and the short range repulsive term Cij/r^12 term. I find the following command in LAMMPS-
pair_style morse/soft 4 0.9 10.0
pair_coeff * * 100.0 2.0 1.5 1.0
pair_coeff 1 1 100.0 2.0 1.5 1.0 3.0
and
pair_style morse 2.5
pair_style morse/smooth/linear 2.5
pair_coeff * * 100.0 2.0 1.5
pair_coeff 1 1 100.0 2.0 1.5 3.0
In these cases, can someone suggest to me how to implement long range coulombic term Z1Z2/r^2 and the short range repulsive term Cij/r^12 term.
Thanks
Mukesh Pandey,
you can add a coulomb interaction to a non-coulomb potential through using pair style hybrid/overlay.
if you want to replace the regular morse potential with a piecewise potential, e.g. LJ repulsion until r_min and morse attraction from r_min to r_cut, then you either need to write your own pair style (in C++) or tabulate your potential and use pair style table for that.
i am a bit surprised why you would want to mix a 12-6 LJ repulsion with a morse attraction, though, since conventional wisdom is that the 12-6 LJ repulsion was chosen for computational efficiency (9-6 would be closer, but requires to use a sqrt() call, which can be avoided with 12-6), and that the morse repulsion is more in line with regular materials. … and since you are not using a plain 12-6 LJ, there is no performance benefit from having the too steep repulsion.
axel.