Universal octahedral-site distortion in orthorhombic perovskite oxides.

Lattice parameters of the orthorhombic perovskites RMO3 (R=rare earth, M=Ti, V, ..., Ni, and Ga) have been simulated based on the ionic M-O bond length and rigid MO6/2 octahedra. Comparison with experimental data shows that the long-standing lattice-parameter anomaly generally found for the larger R3+ ions in these families is caused by a structural feature that is not revealed by the geometric tolerance factor widely used for the perovskites.