106 research outputs found
The Long Journey from Ab Initio Calculations to Density Functional Theory for Nuclear Large Amplitude Collective Motion
At present there are two vastly different ab initio approaches to the
description of the the many-body dynamics: the Density Functional Theory (DFT)
and the functional integral (path integral) approaches. On one hand, if
implemented exactly, the DFT approach can allow in principle the exact
evaluation of arbitrary one-body observable. However, when applied to Large
Amplitude Collective Motion (LACM) this approach needs to be extended in order
to accommodate the phenomenon of surface-hoping, when adiabaticity is strongly
violated and the description of a system using a single (generalized) Slater
determinant is not valid anymore. The functional integral approach on the other
hand does not appear to have such restrictions, but its implementation does not
appear to be straightforward endeavor. However, within a functional integral
approach one seems to be able to evaluate in principle any kind of observables,
such as the fragment mass and energy distributions in nuclear fission. These
two radically approaches can likely be brought brought together by formulating
a stochastic time-dependent DFT approach to many-body dynamics.Comment: 9 page
Some open questions in TDDFT: Clues from Lattice Models and Kadanoff-Baym Dynamics
Two aspects of TDDFT, the linear response approach and the adiabatic local
density approximation, are examined from the perspective of lattice models. To
this end, we review the DFT formulations on the lattice and give a concise
presentation of the time-dependent Kadanoff-Baym equations, used to asses the
limitations of the adiabatic approximation in TDDFT. We present results for the
density response function of the 3D homogeneous Hubbard model, and point out a
drawback of the linear response scheme based on the linearized Sham-Schl\"uter
equation. We then suggest a prescription on how to amend it. Finally, we
analyze the time evolution of the density in a small cubic cluster, and compare
exact, adiabatic-TDDFT and Kadanoff-Baym-Equations densities. Our results show
that non-perturbative (in the interaction) adiabatic potentials can perform
quite well for slow perturbations but that, for faster external fields, memory
effects, as already present in simple many-body approximations, are clearly
required.Comment: 15 pages, submitted to Chemical Physic
The electronic structure of iridium oxide electrodes active in water splitting
Iridium oxide based electrodes are among the most promising candidates for electrocatalyzing the oxygen evolution reaction, making it imperative to understand their chemical/electronic structure. However, the complexity of iridium oxide's electronic structure makes it particularly difficult to experimentally determine the chemical state of the active surface species. To achieve an accurate understanding of the electronic structure of iridium oxide surfaces, we have combined synchrotron-based X-ray photoemission and absorption spectroscopies with ab initio calculations. Our investigation reveals a pre-edge feature in the O K-edge of highly catalytically active X-ray amorphous iridium oxides that we have identified as O 2p hole states forming in conjunction with IrIII. These electronic defects in the near-surface region of the anionic and cationic framework are likely critical for the enhanced activity of amorphous iridium oxides relative to their crystalline counterparts
Brottsofferklander: Har bedömarens kön samt vÄldtÀktsoffrets kön och alkoholhalt betydelse?
VÄldtÀktsoffer kan ibland klandras för vad de utsatts för, sÄ kallat offerklander. I en experimentell studie med designen 2 (Bedömarens kön: man vs. kvinna) à 2 (Offrets kön: man vs. kvinna) à 2 (Offrets alkoholhalt: nykter vs. berusad) fick 275 juriststudenter runt om i Sverige genom en webbenkÀt ta del av en vinjett av ett fiktivt vÄldtÀktsfall för att sedan utdela grad av skuld. NÄgra av hypoteserna var att manliga bedömare skulle skuldbelÀgga i större utstrÀckning samt att manliga samt berusade offer skulle skuldbelÀggas i större utstrÀckning. Studien visade inget stöd för hypoteserna dÄ inga signifikanta skillnader upptÀcktes mellan grupperna. Trots förekomsten av mindre metodologiska betÀnksamheter bidrar studien till vidare förstÄelse för under vilka omstÀndigheter offerklander uppstÄr
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