Quantum-Chemical Modeling of the First Coordination Sphere of the Metal Cation in Monazite

A model of minimum size clusters in orthophosphates has been suggested. In the case of monazite, the cluster includes a cerium(III) cation with nine oxygen atoms of the first coordination sphere, from seven neighboring phosphate anions. Its charge consists of the cation charge QM and the charges of the oxygen atoms QO =–1 a. u. The results of quantum-chemical simulation assume the possibility of the Ce(III) cation substitution with the Th(III), Th(IV) and U(IV) actinide cations. Substitution with thorium is favorable over that with uranium.