[DFTB-Plus-User] DOS Fermi Energy problem

Ezgi Erdogan ezgierdo at gmail.com
Fri Aug 21 13:40:45 CEST 2009


Dear Dr.B.Aradi,

Thank you for warning me the vacumm. That means, I have to use the *.xyz
not to use *.gen file for right unitcell.

Thank you for your support,

Ezgi







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Today's Topics:

  1. Re: DOS Fermi Energy problem (B?lint Aradi)
  2. Re: Hydrides (B?lint Aradi)


----------------------------------------------------------------------

Message: 1
Date: Fri, 21 Aug 2009 08:47:38 +0200
From: B?lint Aradi <balint.aradi at bccms.uni-bremen.de>
Subject: Re: [DFTB-Plus-User] DOS Fermi Energy problem
To: User list for DFTB+ related questions
       <dftb-plus-user at dftb-plus.info>
Message-ID: <4A8E430A.9080003 at bccms.uni-bremen.de>
Content-Type: text/plain; charset="utf-8"

Dear Ezgi,

> I would like to ask you the density of states (DOS) graphics. I have
trouble
> around fermi level.
>
> Now here is my question is coming. In this geometry there should be
confused
> Fermi Energy Level or I am calculating in wrong way? So which Fermi Energy
> Level in this DOS graphics should be done. From detailed.out file we can
> say:  Fermi energy: -0.1837716172 H       -5.000680 eV. To shift +Efermi
> Level or -Efermi Level or just draw this plot between -4  to 4 or what
could
> be other solution? For my further calculation I have to get proper Fermi
> Energy Level and DOS graphs.
>

 The Fermi level, which is spit out by the code is the absolute value of
the fermi level. So, if you want to generate a plot, where the Fermi
level is at zero, you should shift you plot by -Efermi, so in you case,
you'd had to add 5.00680 eV to every value. However, you should be aware
of the fact, that if you have a large gap and zero temperature, the
Fermi energy can be numerically quite unreliable, beeing just somewhere
in the gap. It is, however, not the case with your system.

 Addiotionally, in order to draw a proper DOS, you should use more
K-points to have a better sampling, so I'd suggest to take a higher
K-point sampling. And of course, you have to write the number of
k-points generated by dftb+ for the given scheme into the input file for
dosplot.

 Also I noted, that in your geometry, you have vacuum between the
sheets also along the periodic direction x. I'm not sure, if it was
intended or not.

  Best regards

   B?lint

--
Dr. B?lint Aradi
Bremen Center for Computational Materials Science, University of Bremen
http://www.bccms.uni-bremen.de/en/~b_aradi<http://www.bccms.uni-bremen.de/en/%7Eb_aradi>


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Message: 2
Date: Fri, 21 Aug 2009 08:54:54 +0200
From: B?lint Aradi <balint.aradi at bccms.uni-bremen.de>
Subject: Re: [DFTB-Plus-User] Hydrides
To: User list for DFTB+ related questions
       <dftb-plus-user at dftb-plus.info>
Message-ID: <4A8E44BE.6030203 at bccms.uni-bremen.de>
Content-Type: text/plain; charset="utf-8"

Dear Duncan,

> I have been wondering about the feasibility of using dftb+ for metal
hydride
> systems.
>
> Can any of the developers give me an indication of the time and effort
that
> would be involved in developing a parameter set for such systems?
>
> Is this done from the results of DFT calculations?

 I'm personally not aware about any activities in this direction so far.
Creating new parameters can be quite time consuming, depending how many
elements are involved, and how difficult they turn out to be. As an
example, I can refer to our currently published ZnO + organics set
(znorg), where the current organic set was extended with Zn, in order to
make sure, that also bulk properties of Zn and ZnO are desribed well
enough. It took the PhD-student a few months, to get a reliable set.

 Best regards

    B?lint

--
Dr. B?lint Aradi
Bremen Center for Computational Materials Science, University of Bremen
http://www.bccms.uni-bremen.de/en/~b_aradi<http://www.bccms.uni-bremen.de/en/%7Eb_aradi>



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