Fundamentals of Time-Resolved Charge-Transfer in Time-Dependent Density Functional Theory

TL;DR

This paper investigates the development of step and peak structures in the correlation potential during charge transfer in time-dependent density functional theory, highlighting limitations of common approximations.

Contribution

It reveals the non-local, dynamic features of the correlation potential crucial for accurate charge-transfer modeling, which are missed by standard functionals.

Findings

Exact correlation potential develops step and peak structures during charge transfer.

Standard approximations fail to capture these structures, leading to inaccurate dynamics.

Lack of these features results in the absence of Rabi oscillations in simulations.

Abstract

We show that as an electron transfers between closed-shell molecular fragments at large separation, the exact correlation potential of time-dependent density functional theory gradually develops a step and peak structure in the bonding region. This structure has a density-dependence that is non-local both in space and time, and even the exact ground-state exchange-correlation functional fails to cap- ture it. In the complementary case of charge-transfer between open-shell fragments, an initial step and peak vanish as the charge-transfer state is reached. Lack of these structures in usual approxima- tions leads to inaccurate charge-transfer dynamics. This is dramatically illustrated by the complete lack of Rabi oscillations in the dipole moment under conditions of resonant charge-transfer.