Theoretical study of the relative stabilities of the [alpha]/[[beta].sub.3]-[[X[W.sub.11][O.sub.39]].sup.m-] lacunary polyoxometalates (X = P, Si)

A computational study of the relative stability of the monolacunary Keggin polyoxotungstates [alpha] and [[beta].sub.3]-[[X[W.sub.11][O.sub.39]].sup.m-] (X = P, m = 7; X = Si, m = 8) and the effect of the nature of different grafted cations and of the central anion X[O.sub.4.sup.n-] on the relative stabilities of the lacunary isomers are described. The studies have shown how to favor the formation of [[beta].sub.3] derivatives in future synthesis.