Calculating electronic excitation spectra for large-scale applications
Time dependent density functional theory (TDDFT) has proven to be a powerful standard approach enabling the calculation of excitation energies and excited state properties for medium-sized systems of about 100 atoms. Large-scale applications aiming for broad-band electronic spectra of systems in the size range of several hundreds of atoms are however not routinely feasible within standard TDDFT. In 2013, Grimme therefore proposed a simplified Tamm-Dancoff (sTDA) density functional approach approximating two-electron repulsion integrals using Löwdin monopoles and a semi-empirical Coulomb operator [1]. The sTDA ansatz was assessed for a variety of test sets proving that accuracy loss for excitation energies in comparison to standard TDDFT is negligible while computational savings are increased by two orders of magnitude [2,3]. Based on the original implementation by Grimme, we present an sTDA implementation in the Gaussian and plane waves (GPW) framework of the CP2K program package [4], broadening the application range from molecules to periodic systems. We show benchmark results comparing to standard TDDFT and the original sTDA implementation.
[1] Stefan Grimme, J. Chem. Phys., 2013, 138, 244104.
[2] Jakob Seibert, Christoph Bannwarth, Stefan Grimme, J. Am. Chem. Soc., 2017, 139, 11682.
[3] Stefan Grimme, Christoph Bannwarth, J. Chem. Phys., 2016, 145, 054103.
[4] The CP2K developers group. CP2K is freely available from http://www.cp2k.org/.