  Influences of nonlinear screening on effective interactions between spherical
macroions in charged colloids are described via response theory. Nonlinear
screening, in addition to generating effective many-body interactions, is shown
to entail essential corrections to the pair potential and one-body volume
energy. Numerical results demonstrate that nonlinear effects can substantially
modify effective interactions and thermodynamics of aqueous, low-salt
suspensions of highly-charged macroions.
