[DFTB-Plus-User] Calculation of HOMO and LUMO levels

[Bálint Aradi]

> 
> Thank you for your reply. However when I checked the band.out file, I 
> have few energies with fractional occupancy. And they lie below the 
> Fermi level.

If you have fractional occupations such as for metallic systems, then 
HOMO and LUMO are somewhat ill defined concepts. Probably, the 
Fermi-level is the best thing you can have then. If you wanted, you 
still could do define a HOMO, of course, by counting which would be the 
highest occupied level, if you filled up all levels with integer number 
of electrons until all electrons had been used up, but I am unsure, 
whether that would be a very useful quantity.

Best regards,

Bálint
> 
> On Tue, 13 Jun, 2023, 11:35 am Bálint Aradi, <aradi at uni-bremen.de 
> <mailto:aradi at uni-bremen.de>> wrote:
> 
>     Dear Hemanth,
> 
>     HOMO = highest occupied molecular orbital, LUMO = lowest unoccupied
>     molelular orbital. Occupations of the molecular orbitals can be
>     found in
>     the band.out file. Both levels should be in the vicinity of the
>     Fermi-level.
> 
>     Best regards,
> 
>     Bálint
> 
> 
>     On 13.06.23 07:18, Hemanth Haridas wrote:
>      > Dear all,
>      >
>      > I am trying to calculate the HOMO and LUMO levels of a molecule
>     using
>      > DTB+. However, I could only find Fermi energy in the detailed.out
>     file.
>      > The calculation was performed on the Gamma point. Any pointers on
>     how to
>      > calculate HOMO and LUMO levels would be much appreciated.
>      >
>      > --
>      > *Hemanth H 18310019*
>      > Research Scholar
>      > IIT Gandhinagar
>      >
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> 
>     -- 
>     Dr. Bálint Aradi
>     Bremen Center for Computational Materials Science, University of Bremen
>     http://www.bccms.uni-bremen.de/cms/people/b-aradi/
>     <http://www.bccms.uni-bremen.de/cms/people/b-aradi/>
> 
> 
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-- 
Dr. Bálint Aradi
Bremen Center for Computational Materials Science, University of Bremen
http://www.bccms.uni-bremen.de/cms/people/b-aradi/


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