Real-time (RT) propagation of an electronic density matrix in time following its perturbation by an electric field kick permits the determination of electronic excitation spectra through Fourier transformation of the time-dependent dipole moment. This model has been primarily applied within the context of time-dependent density functional theory (TD DFT), but other effective electronic Hamiltonians can also be employed, e.g., those derived from semiempirical intermediate neglect of differential overlap (INDO) theory. One particular advantage of RT TD DFT is that it can be used with an excited-state density matrix to generate transient absorption (and emission) spectra, for which otherwise more computationally demanding quadratic response theories are typically required. Challenges associated with the RT methodology, on the other hand, include potentially long times to convergence, and limited information with respect to the nature of the individual peaks in the predicted electronic spectrum. Details of our developments to address these challenges, together with example applications to large chemical systems, will be presented.

Some recent developments to accelerate and better characterize electronic excitation spectra from real-time time-dependent electronic structure theories

256th National Meeting (2018)

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