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

First-principle calculations have been completed on a series of Ln(2)Sn(2)O(7) (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-O-48f > bonds in stannate pyrochlores are much more covalent than the < Ln-O-48f > bonds, and a nonlinear relationship is observed between the < Sn-O-48f > or < Ln-O-48f > bond lengths and the Ln cation radii. The < Ln-O-8b > 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. (C) 2007 Elsevier B.V. All rights reserved.