Modeling Electron-Phonon Coupling in Perovskites

Abstract

Electron-phonon coupling plays a central role in determining key material properties, such as carrier mobility and optical response. However, accurately modeling these interactions remains computationally demanding and methodologically complex. In this work, different modeling approaches to electron-phonon coupling are explored and their effectiveness is demonstrated for two prototypical perovskite systems: the halide perovskite cesium lead bromide and the oxide perovskite calcium titanate. For the oxide, the study also includes Ruddlesden–Popper phases. The objective is to understand temperature-dependent electronic properties and to develop models for band edge fluctuations and polarization behavior. For cesium lead bromide, the study focuses on the cubic phase. During molecular dynamics simulations, band gap and valence band maximum data were obtained from density functional theory calculations, and the corresponding phonon mode coordinates were extracted. A feature-based model was developed to describe band edge fluctuations as a func tion of the mode coordinates. Several feature selection methods were tested, and the model was found to adequately capture fluctuations in the valence band maximum using a subset of the total phonon modes. For calcium titanate, tensorial neuroevo lution potential models were trained to predict Born effective charges using density functional theory data from the perovskite structure and two Ruddlesden-Popper phases. Subsequently, predictions were made for Ruddlesden-Popper phases outside of the training set. The predicted Born effective charges were used to calculate spontaneous polarization, and the model successfully reproduced the polarization drop across the ferroelectric–paraelectric phase transitionn