Implementation of Constrained DFT for Computing Charge Transfer Rates within the Projector Augmented Wave Method

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Materials Science

Background:

• Constrained density functional theory (cDFT) combined with Marcus theory is effective for studying charge transfer reactions.
• Standard DFT methods often struggle with self-interaction errors in these systems.

Purpose of the Study:

• To present a general and robust implementation of cDFT within the projector augmented wave (PAW) framework.
• To enable accurate calculations of charge transfer reactions, overcoming limitations of standard DFT.

Main Methods:

• Developed a cDFT implementation using the PAW framework, supporting both LCAO and finite-difference (FD) real-space grid representations.
• Enabled flexible boundary conditions for isolated molecules to periodic systems.
• Extracted electronic coupling and reorganization energy for Marcus theory parametrization.

Main Results:

• The cDFT-PAW implementation accurately models the dissociation of helium dimer cation, a case where standard DFT fails.
• Achieved qualitatively and quantitatively accurate results for charge localization in a diamine cation, outperforming common DFT functionals.
• Demonstrated accuracy comparable to self-interaction corrected DFT and high-level CCSD(T) at lower computational cost.

Conclusions:

• The presented cDFT-PAW method offers a reliable and efficient tool for studying charge transfer reactions.
• This implementation overcomes significant challenges posed by self-interaction errors in standard DFT.
• The method provides accurate results for complex chemical systems at a reduced computational expense.