  In this study, an ab initio calculation is performed to investigate the
uranium solubility in different sites of Gd2Zr2O7 pyrochlore. The Gd2Zr2O7
maintains its pyrochlore structure at low uranium dopant levels, and the
lattice constants of Gd2(Zr2-yUy)O7 and (Gd2-yUy)Zr2O7 are generally expressed
as being linearly related to the uranium content y. Uranium is found to be a
preferable substitute for the B-site gadolinium atoms in cation-disordered
Gd2Zr2O7 (where gadolinium and zirconium atoms are swapped) over the A-site
gadolinium atoms in ordered Gd2Zr2O7 due to the lower total energy of
(Gd2-yZry)(Zr2-yUy)O7. The theoretical findings present a reasonable
explanation of recent experiment results.
