I am modeling the interaction of impurity molecules with crystal surfaces, running geometry optimizations and single-point energy calculations in Forcite to calculate slice and attachment energies. I am modeling the surface with 3D PBCs by inserting a vacuum slab above the surface, and am using the COMPASS forcefield with forcefield-assigned partial charges and the Ewald summation method for vdW and electrostatic forces. Although the crystal system is neutral, the impurity molecules that I add have a +2 charge. Although all of my optimizations have converged and yield intuitive results, I was wondering whether this an issue for the Ewald sum (i.e. shouldn't this result in infinite charge)? I have read about "Uniform Sheet Correction" (http://protomol.sourceforge.net/ewald.pdf), but I am unsure how the Forcite implementation of the Ewald sum treats charged systems.

Thank you!