We extended our .study of heterovalent interfaces between ZnSe(100) and GaAs(100) in superlattices using first-principles, density-functional theory calculations. Here, we concentrate On the changes in interfacial binding energy that occur when the stoichiometry is varied in the anion layer adjacent to the interface. This follows earlier work where the cation stoichiometry was varied. We studied three general categories of simple heterojunctions: those with only As-Zn bonding, those with only Se-Ga bonding, and those with mixed As-Zn and, Se-Ga bonding. We also considered more complex interface configurations. Several - different variations in interfacial stoichiometry that are conceptually based on the heteroepitaxial growth of ZnSe(100) on the GaAs(100)(2 X 4),beta 2 surface structure were studied. In addition, the effects induced by the presence of vacancies -in the vicinity of the surface were investigated. These more complex interfaces are discussed in terms of ' published experimental results. Finally, the possibility that the energy of the interface can be described in terms of the energy of the bonds that span that interface was also examined. We find that, for all of the 14 interfaces studied, the interface energy can be expressed as a simple sum of the per-bond-pair energies with an average error of less than 3%. Therefore, in these systems, the energies, of the interfacial bonds are "additive" to a good approximation. (c) 2005.