TDDFT–Generalized kick perturbations and monitoring observables for calculation of excitation energies

Abstract

This article introduces a generalized way to calculate excitation energies of many-body Hamilton operators by propagating kicked orbitals within time-dependent density functional theory (TDDFT). We use generalized δ(t) perturbations and monitor certain observables of the reduced one-body density to calculate the excitation energies of a static many-particle problem. This generalizes the usual procedure of a linear momentum kick and monitoring the induced t-dependent dipole moment or higher moments. In particular we propose to monitor the time-dependent local charges (e.g. Voronoi, …) in a molecule. As a simple application the S = 0 singlet excitation spectrum of helium is calculated with this formalism included in a standard TDDFT-software package for atoms, QPROP.

Keywords:

• time-dependent density functional theory
• excitation spectrum
• kick perturbation
• time-dependent local charges

Acknowledgements

This work was supported by the Austrian Ministry of Science via its grant for the Wolfgang Pauli Institute and by the City of Vienna Science and Technology Fund (WWTF) via the projects ‘Mathematik und 2004’ MA-04-45 and ‘Mathematik und 2007’ MA-07-11.