Systematic search of materials with high-temperature structural phase transitions: Application to space group P2(1)2(1)2(1)

The existence of a pseudosymmetry in a crystal structure is indicative of a slightly distorted structure of higher symmetry. If the distortion is small enough, it can be expected that the crystal acquires this more symmetric configuration at a higher temperature after a phase transition. The aim of the present study is the development of a general procedure for the Systematic search of pseudosymmetric structures in the available structural databases. The first step is the determination of all relevant supergroups of the space group associated to the known structure. This problem is reduced to the generation of minimal supergroups of space groups using the existing data on their maximal subgroups and normalizers. The determined pseudosymmetry elements are then applied to the crystal structure and a quantitative comparison of the transformed structure acid the original one is performed. Pseudosymmetry is detected when the difference is under a certain threshold. As an example we present the results obtained for inorganic structures with space group P2(1)2(1)2(1) retrieved from the Inorganic Crystal-Structure Database. A significant number of compounds with known phase transitions at high temperatures have been clearly detected as pseudosymmetric with differences between the transformed and the original structures lower than 1.0 Angstrom. About 20 additional structures were detected with pseudosymmetric features under the same threshold. These compounds are considered as having a high probability of exhibiting a phase transition at higher temperatures.