[DFTB-Plus-User] Obtaining band structure and charge distribution

Bálint Aradi balint.aradi at bccms.uni-bremen.de
Thu May 14 08:29:36 CEST 2009

Dear Sougata,

> I have two question regarding DFTB+. One is about to plot band structure and other is about to charge distribution plot of HOMO and LUMO by wave-plot.
>                    Here I have done some calculation on GaAs Nanowire and wanted to plot the band structure. For this firstly I calculate the calculation by 'supercell Folding' with 1x1x4 (with weights 0.0 0.0 0.5) and getting the optimized geometry and proper charge density of the system and then again calculate the calculation by 'KLines' with that optimized geometry and by that proper charge density. That thing is O.K. , Now the question is that in that two calculation I get two different Fermi energy level which is very obvious,  but when I plot the band structure in xmgrace which Fermi energy level I will show in the graph. 
>             The 2nd one is also similar , that here I want to plot HOMO-LUMO charge distribution of the Nanowire at Gamma point. For this firstly I get the proper charge density and optimized geometry , and then by this proper charge density and optimized geometry I calculate single point (Driver{} and MaxSccItaration = 1, ReadInitial Charge = Yes, RestartFrequency=0) calculation at Gamma point and get the detailed.xml and Eigenvec.bin. By this detailed.xml and Eigenvec.bin I plot the charge distribution of HOMO and LUMO by putting Nr. of Kpoints=1 in waveplot_in.hsd. Do I calculate right thing?
>         So Please suggest me about this two things.

 For the Fermi energy, you use the one obtained in the calculation with
the good K-point sampling (first calculation), as this is the
calculation giving you the right density. For the band structure
calculation use set anyway MaxSCCIter=1, so you do not obtain a
convergent density here, just get the band structure for the density
calculated before.

 Yes, your procedure to plot the charge distributions for HOMO and LUMO
in the Gamma point with Waveplot is correct. :-)

  Best regards


Ps. I CCd my reply to the DFTB-Plus-User mailing list. Please post
questions regarding the usage of DFTB+ and Waveplot to this mailing list
(instead of sending it directly to me), so that also other DFTB+ user
can profit from your experiences.

Dr. Bálint Aradi
Bremen Center for Computational Materials Science, University of Bremen

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