title: Calculating core-level excitations and X-ray absorption spectra of medium-sized closed-shell molecules with the algebraic-diagrammatic construction scheme for the polarization propagator.
abstract: Core-level excitations are generated by absorption of high-energy radiation such as X-rays. To describe these energetically high-lying excited states theoretically, we have implemented a variant of the algebraic-diagrammatic construction scheme of second-order ADC(2) by applying the core-valence separation (CVS) approximation to the ADC(2) working equations. Besides excitation energies, the CVS-ADC(2) method also provides access to properties of core-excited states, thereby allowing for the calculation of X-ray absorption spectra. To demonstrate the potential of our implementation of CVS-ADC(2), we have chosen medium-sized molecules as examples that have either biological importance or find application in organic electronics. The calculated results of CVS-ADC(2) are compared with standard TD-DFT/B3LYP values and experimental data. In particular, the extended variant, CVS-ADC(2)-x, provides the most accurate results, and the agreement between the calculated values and experiment is remarkable.
authors.affiliation: Interdisciplinary Center for Scientific Computing, Ruprecht-Karls University, Im Neuenheimer Feld 368, 69120, Heidelberg, Germany.
authors.forename: Jan
authors.initials: J
authors.lastname: Wenzel
authors.forename: Michael
authors.initials: M
authors.lastname: Wormit
authors.forename: Andreas
authors.initials: A
authors.lastname: Dreuw
keywords: CVS-ADC(2); NEXAFS; PTCDA; acenaphthenequinone; bithiophene; core-excited states; electronic structure theory; organic electronics; porphin; thymine; x-ray absorption spectroscopy