Drastically reducing the cost of the XsTD-DFT family of methods using a minimal auxiliary basis set (ηXsTD-DFT) to efficiently treat ultra large systems

To have the most efficient simplified quantum chemistry method to compute excited states and response properties for all-atom quantum mechanical (AQM) methodologies, this contribution introduces the ηXsTD-DFT family of methods for which the exact integral simplified time-dependent density functional theory (XsTD-DFT) is adapted considering the resolution of identity (RI) approximation with a minimal auxiliary basis set. This auxiliary set is composed of 1s orbitals with the square of the atomic