Date/Time
Date(s) - Mar 2 2017
12:00 AM - 2:30 PM
Location
Redwood Rooms C/D, Building 48
Category(ies)
X-ray Spectroscopy Theory Lectures
John J. Rehr
Adjunct Professor of Photon Science, SLAC
and
Dept of Physics, University of Washington
III Inelastic losses and Many-body effects
IV Real-time approaches
The first two parts of this series covered: I) Introduction to X-ray Spectroscopy Theory, and II Real-space Green’s function Theory and FEFF. Now we aim to cover some more advanced aspects of the theory. Lecture III is devoted to many-body effects which are essential to quantitative investigations of XAS. Recent advances now permit parameter-free calculations of the key effects [1]. Physically, they arise from electronic correlations and atomic vibrations that lead to inelastic losses and damping. Quasi-particle (QP) approaches with a GW self-energy such as the GW/Bethe-Salpeter equation [2] and the introduction of vibrational damping with Debye-Waller factors [3] yield significant improvements. Additional losses such as multi-electron excitations can be treated using cumulant-expansion techniques and the quasi-boson approximation [4]. Next, Lecture IV) describes real-time approaches, which are becoming increasingly important in photon spectroscopies ranging from linear and non-linear optical response to XAS with pulsed sources. Here we discuss methods based on real-time, time-dependent density functional theory (RT-TDDFT) and time-correlation functions. Finally we discuss a real-time approach for calculations of dynamic structure in nano-scale materials base on finite-temperature density functional theory based molecular dynamics and the real-space Green’s function approach in FEFF9. This approach is illustrated for the case of supported Pt nanoclusters [5].
[1] John J. Rehr et al., Comptes Rendus Physique 10, 548 (2009).
[2] K. Gilmore et al., Comput. Phys. Comm. 197, 109 (2015).
[3] F. Vila et al., Phys. Rev. B 78, 121404(R), (2008).
[3] Jianqiang Sky Zhou et al., J. Chem. Phys. 143, 194109 (2015).
[4] Y. Takimoto et al., J. Rehr, J. Chem. Phys. 127, 154114 (2007).
[5] A.I. Frenkel et al., J. Vac. Sci. Technol. A 32, 020801 (2014).
