Dear Sunghwan, That's my guess. If you set occupations='fixed' (the default) for the ground state calculation, the turboTDDFT will not complain that your system is metallic. If your system has a 0.5 eV gap there will not be any problem. If the gap goes below 0.1 eV it migh be hard or impossible to converge the ground state calculation with occupations='fixed'. In that case the turboTDDFT cannot be used. According to me as long as the ground state energy converges with occupations='fixed' the turboTDDFT will run smoothly and give reasonable results for your nanoparticles. Once again this is my guess, you should try. Best, Dario
On Sat, Jul 23, 2016 at 6:45 PM, SungHwan Choi <[email protected]> wrote: > 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 >> > > > _______________________________________________ > 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
