Optimal transition states for polaron hopping transport without supercells

Polaron formation localizes charge carriers and drives a crossover from band-like to hopping transport in materials. Hopping dynamics can be obtained from DFT supercell calculations of transition states, but these suffer from polaron self-interaction, spurious electrostatics, and poor scaling with polaron size. We introduce a supercell-free framework for ab initio polaron hopping transport based on the ab initio polaron equations formalism, its variational formulation, and the string method. The approach avoids explicit real-space DFT supercell calculations: it optimizes transition states directly in reciprocal space and provides the polaron configurations along the path, enabling the evaluation of adiabatic hopping rates and mobilities. We apply the method to LiF and rutile TiO₂, revealing multi-step and anisotropic hopping mechanisms. In rutile TiO₂, we compare the computed electron-polaron mobility with experiments and with alternative first-principles approaches. Our results establish a scalable route to first-principles polaron-hopping dynamics in materials in which charge motion is governed by self-trapping.

This archive contains the data necessary to reproduce the results of the latest version of the "Optimal transition states for polaron hopping transport without supercells" article by Vasilii Vasilchenko, Matteo Giantomassi, Samuel Poncé, and Xavier Gonze.