Various mechanisms by which flat, stepped, or kinked surfaces of Ag halides could participate in the generation of interstitial or vacancy Ag ions were considered. In the energetically favored mechanism, surface sites ionized so as to generate an adsorbed Ag ion and a vacancy. The former had a lower energy requirement for exchange into the bulk than did the latter, as deduced from the present calculations. Positive kink sites required the lowest overall energy for this generation step, as compared with flat {100} or stepped {105} surfaces. The nature of the space-charge layer, which involved surface negative charge and sub-surface Ag ions, agreed well with experimental observations. Energies were computed for these processes, and a preliminary estimate was made of the entropy of formation of point defects from the AgBr surface. A calibration of this procedure was carried out for NaCl surfaces, and the calculated energies of formation were found to exhibit excellent agreement with experimental enthalpy values for vacancies.

R.C.Baetzold: Physical Review B, 1995, 52[15], 11424-31