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Structural variation and disorder in bulk materials (mainly halide and oxide perovskites)
Surfaces and interfaces - DFT and Bayesian-optimization-based machine learning
Alloys (mainly halides and oxides) - DFT-based machine learning and structure search
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The most common materials in ferro- and piezoelectrics are oxide perovskites (ABO3). Major characters of oxide perovskites compared with their halide counterparts (ABX3) include the higher valences, relatively smaller B-site (but not A-site) cations, and noticeably more compositional possibilities. As a result, different lattice distortion modes lead to various polarization patterns and thus ferro-, piezo-, and pyroelectric properties. In addition, alloying is very common in this field, and composition-, temperature-, and pressure-dependent multiphase feature plays a decisive role.
The major focus of our study on oxide perovskites is on their crystal and atomic structure. For unalloyed materials as starting points, we wish to have an overview of the material phase space in terms of atomic configurations which reflect different polarization patterns. Starting from these pictures, we further construct alloys and discuss structural variation as a function of composition and other parameters.