TD-DFT without wavefunctions

We present an extension of Orbital-Free Density Functional Theory (OFDFT) to the time domain (TD-OFDFT). The method hinges upon approximating the wavefunction of the system by a single effective orbital augmented by a position-dependent phase factor. We find that such a simplified picture still delivers good optical spectra and response properties for metal clusters, surfaces and bulk systems. Specifically, we show that the method delivers plasmonic collective electronic excitations of metal clusters in reasonable agreement with Kohn-Sham TD-DFT. Because of the simplicity of the model, and the efficient codebase [1], the simulations are extremely computationally efficient delivering converged results in wall-times two or more orders of magnitude smaller than conventional Kohn-Sham TD-DFT.

[1] X. Shao, W. Mi, K. Jiang, A. Genova and M. Pavanello, in preparation.