[Pw_forum] analysis of TDDFPT results

[Timrov Iurii]

Dear Dr. Sergi Vela,


With the current implementation of the Lanczos algorithm in the turboTDDFT program it is not possible to perform analysis of the origin of individual peaks in the absorption spectrum. However, such an analysis can be done using another flavor of the turboTDDFT code, namely the turbo_davidson.x program. More information can be found in this publication:


X. Ge, S. J. Binnie, D. Rocca, R. Gebauer, and S. Baroni, "turboTDDFT 2.0-Hybrid functionals and new algorithms within time-dependent density-functional perturbation theory", Comput. Phys. Commun. 185, 2080 (2014).


With the so-called turboDavidson code (turbo_davidson.x) you can compute  the absorption spectrum (the same as with Lanczos) but as a plus in the output file you will find the information about the origin of the peaks (from which occupied level to which empty level there was a transition and what is the corresponding intensity etc.). However, if you are interested in computing the spectrum in a very wide energy range, then turboDavidson becomes too expensive, and hence it is recommended to use the Lanczos algorithm (at the cost described above, i.e. no information about the origin of the peaks).


HTH


Best regards,

Iurii


--
Dr. Iurii Timrov
Postdoctoral Researcher
Swiss Federal Institute of Technology Lausanne (EPFL)
Laboratory of Theory and Simulation of Materials (THEOS)
CH-1015 Lausanne, Switzerland
+41 21 69 34 881
http://people.epfl.ch/265334
________________________________
From: pw_forum-bounces at pwscf.org <pw_forum-bounces at pwscf.org> on behalf of Sergi Vela <sergi.vela at gmail.com>
Sent: Friday, May 20, 2016 10:30 AM
To: PWSCF Forum
Subject: [Pw_forum] analysis of TDDFPT results

Dear QE users and developers,

I've successfully performed a TDDFPT (Lanczos approach) calculation on a system of my interest, and now I would like to analyze the different bands of the resulting spectrum. I would like to ascribe them to chemical (orbital-excitations, charge-transfer) processes such as I would do when using standard TDDFT codes.

I'd like to know if this is indeed possible and, if so, I'd appreciate some information on how to do it.

All my best,
Dr. Sergi Vela,
Laboratoire de Chimie Quantique, Universitè de Strasbourg, France
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