[DFTB-Plus-User] questions about DFTB+

[Bálint Aradi]

Dear Lida Ansari,

  the DFTB-Plus-User mailing list is the right forum to post any
questions regarding the usage of DFTB+. I'll forward your mail there,
please use this in the future.

> 1) I wonder if it is possible to set fractional charge for dopant(s) in
> DFTB+?

 You can set your system to have a fractional net charge. As the manual
indicates, the Charge keyword expects a real number.

> 2) I used Filling = Fermi {Temperature [K] = 0} for calculation of
> e-structure. Then, in order to see the effects of temperature I set this
> script to 300 (K) but there is little change in the e-structure and
> occupations.  I just want to ask if the electronic temperature parameter
> affects the final results, or is only used to speed convergence?  Also,
> are there any other options in DFTB that I have to use to set finite
> temperature?

 Depends on your system, if you have a wide band gap or HOMO-LUMO gap,
setting 300 K won't change much. If you have a metallic or nearly
metallic system, effects in total energy and eventually even in geometry
relaxation could be seen. This differs in no respect from any ab initio
codes using temperature.

  Best regards

  Bálint

-- 
Dr. Bálint Aradi
Bremen Center for Computational Materials Science, University of Bremen
http://www.bccms.uni-bremen.de/en/~b_aradi


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