Machine learning for exploring small polaron configurational space

Published in npj Computational Materials

Polaron defects are ubiquitous in materials and play an important role in many processes involving carrier mobility, charge transfer and surface reactivity. Determining small polarons’ spatial distributions is essential to understand materials properties and functionalities. However, the required exploration of the configurational space is computationally demanding when using first principles methods. Here, we propose a machine-learning (ML) accelerated search that determines the ground state polaronic configuration. The ML model is trained on databases of polaron configurations generated by density functional theory (DFT) via molecular dynamics or random sampling. To establish a mapping between configurations and their stability, we designed descriptors modelling the interactions among polarons and charged point defects. We used the DFT+ML protocol to explore the polaron configurational space for two surface-systems, reduced rutile TiO2(110) and Nb-doped SrTiO3(001). The ML-aided search proposes additional polaronic configurations and can be utilized to determine optimal polaron distributions at any charge concentration.

The full article can be found here (or directly as PDF).

Viktor Birschitzky, Florian Ellinger, Ulrike Diebold, Michele Reticcioli, and Cesare Franchini

P07 – Polaron pattern recognition in correlated oxide surfaces
P02 – Surface structure and reactivity of multi-component oxides at the atomic scale