[Pw_forum] Turbo TDDFT for a quantum dot

SungHwan Choi sunghwanchoi91 at gmail.com
Sat Jul 23 03:37:59 CEST 2016

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?

Sunghwan Choi

Sunghwan Choi
Ph.D candidate
Computational Quantum Molecular Science Lab
Department of Chemistry, KAIST, Republic of Korea
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