pair_modify shift yes


I wanted to use F3C water potential in my MD simulations, which uses typical form for truncation shift function. I wanted to check if lammps uses the same (for its pair_modify shift yes function), or i need to modify it. I tried looking for .cpp file which does this, but could not find it. Could anyone tell me in which file this calculation is hidden?

Thanks a lot!

The shifting is done in the pair*.cpp file for each pair style that
supports it. E.g. pair_lj_cut.cpp. Look for code using "offset"
which is the amount of the applied shift for each atom type pair.


Thanks, Steve. Offset seems to be referring to shift for LJ potential. While that helps, I also want to define truncation shift for Coulombic interactions. I could not find corresponding offset in pair_lj_cut_coul_long.cpp?

Also what is the default value of constant C (for Coulombic interactions) that lammps takes ?


For any coul/long potential there is no shift, as it is not

The C is simply the conversion factor from qq/r to the native
units system like Kcal/mole. You don't have to worry
about it - LAMMPS handles it for you.