Examining the Effect of Exchange-Correlation Approximations in First-Principles Dynamics Simulation of Interfacial Charge Transfer.

Abstract

We examine the extent to which the exchange-correlation (XC) approximation influences modeling interfacial charge transfer using fewest-switches surface hopping (FSSH) simulations within the single-particle description. A heterogeneous interface between a lithium ion and an extended boron-nitride sheet was considered here, being an extreme case in which wave function localization and energy level alignments are highly sensitive to the XC approximation. The PBE0 hybrid XC approximation yields nonadiabatic couplings (NACs) that are significantly smaller than the values obtained from the PBE-GGA approximation by an order of magnitude for localized electronic states. This difference between the two XC functionals for the calculated NACs was found to derive mainly from the wave function characteristics rather than from the lattice movement although first-principles molecular dynamics trajectories, along which NACs are obtained, differ noticeably between the two XC functionals. Using the NACs and single-particle energy level alignments at different levels of theory, FSSH simulations were performed to model the electron transfer dynamics at the interface. The electron transfer time scale was found to vary as much as, but not more than, 1 order of magnitude. The time scale was found to be quite sensitive to both NACs and energy level alignments. While the order of magnitude consistency for the charge transfer rate is encouraging even for this rather extreme model of heterojunction interface, continued advancement in electronic structure methods is required for quantitatively accurate determination of the transfer rate.