Static lattice computer simulations have been used to study the distributio
n of Nd(III) and the alkaline earths, Ca, Sr and Ba, in ion exchanged beta"
-alumina. The site preferences for Nd are found to depend on the symmetry o
f the Nd-sodium vacancy complex: highly symmetric configurations favour the
Na cation site, whereas lower symmetry structures lead to occupancy of the
mid-oxygen site. The alkaline earths site preferences depend largely on io
n size, with Ba occupying sodium sites and Ca preferring mid-oxygen positio
ns. Sr is found to occupy either site, depending on the local symmetry.