Scientific Computing Seminar

Date:

Friday, December 3, 2004

Time:

1:00pm-2:00pm

Location:

50A-5132

Seminar Speaker:

Fan Zhang
Department of Physics & Astronomy
Rutgers University

Title:

Double excitations within time-dependent density functional theory linear response

Abstract:

Time-dependent density functional theory (TDDFT) is a very efficient method to solve the excitation properties in chemical and solid-state physics. Although in principle TDDFT yields excitations of any number, only a fraction of these (those spanned by the single excitations) can be obtained when using an adiabatic exchange-correlation kernel: In order to produce double excitations, the exact exchange-correlation kernel has a very strong frequency-dependence near the double excitation.

We construct a model for this and derive the exact frequency-dependent kernel when a double excitation mixes with a single excitation, well separated from the other excitations, in the limit that the electron-electron interaction is weak. We construct a dressed TDDFT method, which is a nonempirical approximation for the general case, and illustrate our results on a simple model: two Fermions in a one-dimensional parabolic well, interacting via a delta-function repulsion. Finally, we apply the dressed TDDFT method to the calculation of 2^1A_g states of the shortest polyenes.

Sponsor of Seminar:

Lin-Wang Wang

Scientific Computing

Contact Esmond G. Ng EGNg@lbl.gov