Dear Sunghwan, I have not used the code on systems with the characteristics you describe. This is my guess: As far as the ground state of your quantum dot converges without a smearing the turboTDDFT code can be used and will be stable. While the independent electron polarizability of a 0 gap system diverges for \omega-->0, the Hartree part in the TDDFT kernel will increase the value of the gap and/or will "push" the oscillator strength to higher energies. Best, Dario
On Fri, Jul 22, 2016 at 6:37 PM, SungHwan Choi <[email protected]> wrote: > Dear all, > I am checking whether turboTDDFT program is suitable for my project. My > project is to calculate absorption spectrum of metallic quantum dot. I have > two questions. > > 1) From other post, I read the fact that turboTDDFT cannot calculate a > metallic system. Here, how do we define metallic system? just system that > have no band gap? then for small metallic quantum dot can be a non-metallic > system since it has small band gap (0.1~0.5eV). case that fractional > occupation does not happen? then, we can control the occupation parameter > not to make fractional occupation. > > 2) A metallic quantum dot has a size-dependency for band gap. Thus, if > size become larger, then band gap become narrow. When turboTDDFT failed to > predict an absorption spectrum? and do you know a numerical trend of > artifact, which come from low band gap? > > By the way, does this limit come from algorithm or implementation of > turboTDDFT? As far as I understood there is no limit of algorithm itself. I > think there is some practical issues on there. Would you tell me where some > troubles come up? > > Sincerely > Sunghwan Choi > > > ======================================== > Sunghwan Choi > Ph.D candidate > Computational Quantum Molecular Science Lab > Department of Chemistry, KAIST, Republic of Korea > > > _______________________________________________ > Pw_forum mailing list > [email protected] > http://pwscf.org/mailman/listinfo/pw_forum >
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