In this talk, I will show that a subsystem formulation of DFT can simplify both the theoretical framework and the computational effort for calculating the electronic structure of condensed phase systems. I claim that the naturally subsystem-like form of molecular aggregates makes subsystem DFT a better descriptor of the underlying physics than regular DFT of the supersystem.I will present a novel van der Waals DFT theory based on the Frozen Density Embedding formulation of subsystem DFT (FDE-vdW) and, thus, theoretically exact and amenable to sensible approximations. Application of FDE-vdW to the S22 benchmark set provides proof-of-principle for the dramatic improvement of this theory over semilocal subsystem DFT.I will also present an extension of the semilocal subsystem DFT to treat diabatic states. I will discuss effective methods to calculate the electronic coupling between diabatic states, as well as a prescription to calculate superexchange couplings in unprecedentedly large systems, such as solvated DNA. Applications include an all-electron model of hole transfer in explicitly solvated DNA oligomers by QM waters that includes the description of dynamical and non-Condon effects.

Van der Waals interactions and charge transfer excitations made simple by subsystem DFT

248th National Meeting (2014)

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