The pair styles you mention (coul/…/soft or tip4p/…/soft) contain just the Coulomb part, analogous to the pair style coul/cut, etc. Their purpose is to be combined with a repulsive part.
Full pair potentials are available in pair styles lj/cut/coul/long/soft, etc. for those applications using typical repulsive+dispersive+electrostatic potential combinations.
The core-softed versions are just modifications of existing pair styles, so it is a good idea to read the man pages for both.
Hope this helps.
Subject: [lammps-users] Free energy of water
Date: 26 June 2017 at 14:50:29 GMT+2
Dear LAMMPS users ,
I want to calculate water free energy by fix adapt/fep command .
The coul/cut/soft, coul/long/soft and tip4p/long/soft substyles are designed to be combined with other pair potentials via the pair_style hybrid/overlay command. This is because they have no repulsive core. Hence, if used by themselves, there will be no repulsion to keep two oppositely charged particles from overlapping each other. In this case, if lambda = 1, a singularity may occur.
According to the above mentioned description can you please let me know how I can do this calculation ?
Actually I am not completely familiar with this Fix command I have started reading some papers , I would be grateful if you also can give me some hints about that .