September 20th

 

when: Thursday 20/09/2018, 10:30
where: KE E-541 (møterom)
speaker: Thomas Frauenheim (Bremen Center for Computational Materials Science, University of Bremen)
title: Atomistic modeling of quantum processes in nanoscale devices
abstract:
The new release of DFTB+ as a density-functional (DFT)-based approach, combining DFT-accuracy and Tight-Binding (TB) efficiency, is reported; http//:www.dftb.org. Methodological details and recent extensions to improve reliability and accuracy will be described. Advanced functions include spin degrees of freedom, time dependent methods for excited states, non-adiabatic electron-ion dynamics and quantum transport calculations under open boundary conditions using non-equilibrium Green´s function methods. The major focus of the talk will be on the time-dependent DFTB extensions. I am going to present the first real-time atomistic simulation on the quantum dynamics of plasmon excitations in icosahedral silver nanoparticles under strong laser pulses. We identify the emergence of sub-picosecond breathing-like radial oscillations starting immediately after laser pulse excitation, with increasing amplitude as the field intensity increases. The ultrafast dynamic response of nanoparticles to laser excitation points to a new plasmon assisted mechanism rather than longer time-scale equilibrium electron-phonon scattering previously assumed. The TD-DFTB implementation in real time domain also allow to simulate transient absorption spectra (TAS) fully atomistically. When this technique is applied to the study of ultrafast dynamics of Soret-excited zinc(II)-tetraphenylporphyrin in the sub-picosecond time scale, quantum beats in the transient absorption caused by impulsively excited molecular vibrations are observed. As last examople ultrafast electron transfer in P3HT-PBCM organic blends will be demonstrated to become enhanced by the nuclear motion and under open boundary conditions with applied bias, see example below.
Example
(The abstract including speaker's short CV can be dowloaded here).

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