Figure 2: (a) Contour plot in the CuO plane of the displacement-induced charge density redistribution for the mode within the rigid ion model (RIM) for . (b) Same as (a), but for the nonlocal part of the charge response in the optimally doped state due to nonlocal EPI effects in the half-breathing mode . The displaced ions are indicated by a dot with an arrow. Full lines (—) mean that electrons are accumulated in the corresponding region of space and the broken dotted lines ( ) indicate regions where the electrons are pushed away. is given in units of .