Minimum Energy Paths for Non-Adiabatic Charge Transitions in Oxide Defects

Charge transfer between oxide defects and device substrate can be described as a non-radiative multiphonon transition. Within this approach oxide defects are usually modelled as 1-dimensional harmonic oscillators. In the classical limit the charge transition dynamics are determined by the crossing point of the corresponding diabatic potential energy curves of the defects. In this work we go beyond the harmonic approximation and present a scheme to locate the minimum energy path between two differently charged defect configurations on multidimensional potential energy surfaces obtained with density functional theory. Using this more accurate method we quantify the accuracy of the harmonic approximation and demonstrate its applicability for common defects in amorphous silica. Furthermore, we compare the resulting transition barriers with experimental data and demonstrate excellent agreement for hydrogen-related defect species.