Coulomb cutoff for ion

GROMACS version:2020.1
GROMACS modification: No
I have a rudimentary question regarding the calculation of solvation energies of charged species. Most examples so far seem to use a Coulomb cutoff of 1 nm or 1.2 nm for neutral species. For charged species, does the Coulomb cutoff need to be longer? Also, should the box size be increased accordingly? Or do I not need to worry about it since most interactions are cancelled during the DG calculation? Thank you very much.

The cutoff is dictated by the force field and its conventions, not the chemical nature of the species. With PME, the electrostatic cutoff doesn’t matter a whole lot but you should remain consistent with the underlying force field, otherwise you risk breaking its assumptions and balance between LJ and electrostatic contributions.

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Thank you very much for clarification!!