Prediction of the crystal structures of perovskites using the software program SPuDS

The software program SPuDS has been developed to predict the crystal struct ures of perovskites, including those distorted by tilting of the octahedra. The user inputs the composition and SPuDS calculates the optimal structure in ten different Glazer tilt systems. This is performed by distorting the structure to minimize the global instability index, while maintaining rigid octahedra. The location of the A-site cation is chosen so as to maximize t he symmetry of its coordination environment. In its current form SPuDS can handle up to four different A-site cations in the same structure, but only one octahedral ion. Structures predicted by SPuDS are compared with a numbe r of previously determined structures to illustrate the accuracy of this ap proach. SPuDS is also used to examine the prospects for synthesizing new co mpounds in tilt systems with multiple A-site coordination geometries (a(+)a (+)a(+), a(0)b(+)b(+), a(0)b(-)c(+)).