Structural and bonding properties of stannate pyrochlores: A density functional theory investigation

First-principle calculations have been completed on a series of Ln2Sn2O7 (Ln = Sm, Gd, Tb, Ho, Er, Lu, Y, La, Pr and Nd) pyrochlores to study the effect of structural geometry and bond-type on the stability of the pyrochlore structure-type. Overlap population analysis showed that the 〈Sn–O48f〉 bonds in stannate pyrochlores are much more covalent than the 〈Ln–O48f〉 bonds, and a nonlinear relationship is observed between the 〈Sn–O48f〉 or 〈Ln–O48f〉 bond lengths and the Ln cation radii. The 〈Ln–O8b〉 bonds are the most ionic among the metal–oxygen bonds. These results are consistent with experimental results. We note other factors, in addition to bond-type, that affect the stability of the pyrochlore structure.