[CP2K-user] Bulk Silicon Tddft

Matt W mattwa... at gmail.com
Mon Mar 29 15:35:00 UTC 2021

Your tddft states seem to coincide with the HOMO-LUMO gaps of the different 
systems - as they should for delocalised bulk states. That the HOMO-LUMO 
values are small seems could suggest the LUMO calc has not converged 
(maybe) or that your geometry is not replicating correctly?

On Monday, March 29, 2021 at 2:10:37 PM UTC+1 Laurens wrote:

> Dear all,
> I am trying to do tddft simulations of bulk silicon (please see attached 
> band structure and in/output files).
> Since tddft is not implemented for k-points, I have tried using supercells 
> of sizes up to and including 5x5x5 times the primitive unit cell.
> This changes the lowest excitation energy, but unfortunately the lowest 
> excitation energy does not seem to converge to a value close to the 
> calculated bandgap of 0.7 eV: the lowest excitation energy decreases from 
> an energy of 2.2 eV for the single unit cell, to an energy between 0.28 eV 
> (4x4x4 cell) and 0.85 eV (3x3x3 cell).
> Does anybody have any suggestions on tddft simulations of bulk solids?
> Best regards,
> Laurens
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