In polymers and solids, a cutoff distance, in Ångstroms, is needed in order to ensure that
every atom has a correct electric environment. If no cutoff is set, then
equivalent atoms would experience different electric fields. The CUTOFP
distance is set, by default, to the largest distance that would ensure that
equivalent atoms experience the same potential. In calculating the potential
due to distance atoms, atoms separated by more than CUTOFP are treated
as if they were at distance CUTOFP.