Cutoff radius of Coulomb force

GULP
1

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,
Junwei

2

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.
Regards,
Julian

3

Thanks very much.