[Pw_forum] Turbo TDDFT for a quantum dot

[SungHwan Choi]

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
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