Pair potentials for metal oxides...

 Dear All:
 We are interested in obtaining pair potentials useful for a preliminary
 discussion of the properties of ionic systems, specifically metal oxides.
 In papers by Ziemann and Castleman I have found pair potentials for MgO.
 Does anyone know of similar pair potentials for CaO, SrO, and BaO ??
 All responses will be welcome. Thank you in advance.
 Andres Aguado
 aguado \\at//