Dear Dario, Thank you for a kind reply. You mean that if it is converged without smearing option, then there is no problem on doing turboTDDF calculation. Am I correct? Sincerely, Sunghwan Choi
======================================== Sunghwan Choi Ph.D candidate Computational Quantum Molecular Science Lab Department of Chemistry, KAIST, Republic of Korea 2016-07-23 16:43 GMT+09:00 dario rocca <[email protected]>: > 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 >> > > > _______________________________________________ > Pw_forum mailing list > [email protected] > http://pwscf.org/mailman/listinfo/pw_forum >
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