Cutoff radius of Coulomb force

Dear Julian,

I want to describe the interatomic potential of ionic crystals using Coulomb potential and Buckingham potential. I wonder if I can specify the cutoff radius manually for the Ewald calculation, that is, if r is less than the cutoff radius the coulomb interaction will be calculated in lattice sums (real space). I found the default cutoff radius in GULP is 12 angstrom.

Thanks very much.
Best regards,

Dear Junwei,
To understand the issues around cutoffs and electrostatics you need to read the section in the manual on the Ewald sum (for 3-D periodic systems) as it’s not as simple as giving a cutoff radius as per short-range potentials.

Thanks very much.