Projection-based quantum embedding methodologies provide a framework for performing DFT-in-DFT and wavefunction-in-density functional theory (WF-in-DFT) calculations. The previous application of using absolute localization on the ground states of molecular systems1 and periodic systems2 showed high accuracy and improved computational efficiency. In this work, we extend the absolute localization method to study localized excited states using the equation of motion coupled cluster singles and doubles (EOM-CCSD) and time-dependent density functional theory (TDDFT). The embedding results on small molecular systems show that EOM-CCSD-in-DFT and TDDFT-in-DFT are highly accurate compared to the corresponding canonical EOM-CCSD and TDDFT results. Additionally, the absolute localization method also can eliminate spurious low-lying excitation energies from charge-transfer states, which is one of the well-known shortcomings of TDDFT. Furthermore, we attempt to capture the environment response triggered by the electronic excitations happened in the active subsystem using a new relaxation scheme with a state-averaged approach. However, this scheme always lowers the excitation energies due to unrealistic relaxation of the slow polarization component of the environmental response. We apply absolute localization method to a large biological system, green fluorescent protein (GFP). The results show that absolute localization is systemically improvable and accurate for local excitations. Our method provides the accuracy of computationally expensive methods like EOM-CCSD to large molecular systems at significantly reduced computational cost.

Quantum embedding for excited states in molecules and solid states: A state-averaged approach

2019 Spring National Meeting

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