This variable controls whether the dipole is calculated at the end of a self-consistent iteration. For finite systems the default is yes. For periodic systems the default is no, unless an electric field is being applied in a periodic direction. The single-point Berry`s phase approximation is used for periodic directions. Ref: E Yaschenko, L Fu, L Resca, and R Resta, Phys. Rev. B 58, 1222-1229 (1998).