Figure 8.
Analytic and finite-difference gradients for a neutral, polarizable cavity fixed at the origin and a sphere with unit positive charge vs. separation using the direct polarization model. Both spheres have a radius of 3.0 Å. The gradient can be seen to approach zero at a number of points, notably when the spheres are separated by approximately 1.5 Å leading to a maximum in the reaction field produced by the charge at the polarizable site, and again when the spheres are superimposed and the reaction field is zero at the polarizable site.