[DFTB-Plus-User] Is Fermi Level calculation reliable for molecules?

[siddheshwar chopra]

Dear Bálint,
Thank you for the proper explanation and help. Actually Fermi level
discussion ( along with the PDOS) is needed in transport mechanism. Thats
the reason of asking.
Kind Regards,

On Fri, Aug 24, 2018 at 12:24 PM Bálint Aradi <aradi at uni-bremen.de> wrote:

> Dear S. Chopra,
>
> On 08/24/2018 07:35 AM, siddheshwar chopra wrote:
> > Dear All,
> > I am using DFTB+ for molecules and polymer studies. I need to study the
> > states around the Fermi levels.
> > I want to confirm if the Fermi level energy mentioned in the
> > "detailed.out" file reliable?
>
> Reliable in which sense?
>
> The Fermi level you obtain in detailed.out is the chemical potential,
> which is needed in order to obtain a neutral system (or a system with
> the specified amount of net charges) while filling up the energy levels
> according to the selected filling function.
>
> In case, you have a system with a large gap and very low electronic
> temperature, the position is numerically ill defined, as shifting the
> Fermi level in the gap may leave the occupations numerically unchanged.
>
> As soon as the gap is smalle enough or the temperature is high enough,
> so that you have excitations (levels with less than 2 electrons below
> the Fermi level and levels with more than 0 electrons above), the Fermi
> level position is well defined.
>
>   Best regards,
>
>   Bálint
>
>
> --
> 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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-- 
*Dr. Siddheshwar chopra,*


*M.Sc., Ph.D (Physics)Assistant Professor (Physics),*
*Amity University, Noida, India.*
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