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O: Fachverband Oberflächenphysik

O 87: Focussed session: Theory and computation of electronic structure: new frontiers VII (jointly with HL, DS)

O 87.2: Vortrag

Donnerstag, 17. März 2011, 17:45–18:00, TRE Phy

Discontinuities of the Exchange-Correlation Kernel and Charge-Transfer Excitations in TDDFT — •Maria Hellgren and Eberhard K.U. Gross — Max-Planck-Institute of Microstructure Physics, Weinberg 2, Halle, Germany

An intriguing consequence for density functional theory (DFT) arises when considering ensembles with densities integrating to fractional particle number. The total ground-state energy as a function of particle number consists of straight-line segments and, consequently, the corresponding exchange-correlation (XC) potential jumps discontinuously. This feature of the exact theory turns out to be a key property to incorporate in approximate functionals in order to obtain, e.g, accurate band-gaps of solids and correct molecular dissociation limits.

It has been demonstrated that the discontinuous nature of the static XC potential naturally carries over to the XC potential of time-dependent density functional theory (TDDFT) appearing in, e.g., time-resolved ionization processes. How the same property is reflected in the XC kernel, defined as the functional derivative of the XC potential with respect to the density, has, so far, not received any attention. The XC kernel is of fundamental importance in TDDFT as it gives access to the particle conserving excitation spectrum. In this work we have investigated the discontinuities of the XC kernel and found them to be crucial for the description of long-range charge-transfer excitations.