Calculations of various sulfur-containing centers adsorbed to sites on the AgCl surface are presented. A density functional method followed by a classical lattice ion relaxation is employed in this work. Several different centers such as Ag₄S₂ have energy levels positioned to trap holes, while Ag₃S⁺ and Ag₅S₂⁺ have levels positioned to trap electrons. It is found that a sulfide ion at a kink site that is compensated by interstitial silver ion undergoes relaxation in the presence of an electron leading to a trap depth of several tenths of an electronvolt. It appears that this may be an important step in chemical sensitization. These results are consistent with stepwise addition of electrons and silver ions resulting in latent image formation.