[DFTB-Plus-User] band structure SCC convergence

Jan M. Knaup Jan.Knaup at bccms.uni-bremen.de
Wed Jul 11 11:14:24 CEST 2012


Dear Rodrigo,

the band_tot.dat file is structured to be very convenient to plot. The
first column is the k-point number and will serve as your x-axis. You can
use the index to apply the usual \gamma, K, L etc labels corresponding to
your input file. The other columns contain the energies for the eigenstates
at the corresponding k-point.

Practically, you can plot the bant_tot.dat file e.g. by importing it into
xmgrace as an NXY data set. (data->import ascii-> change XY to NXY). Or you
can use a command like
"plot for [i =2:XXX]  'bant_tot.dat' u 1:i with lines notitle"
in gnuplot 4.4 or higherm where you replace the XXX by the number of
columns in the file (should be the same as (N_el/2)+1 ).

Hope that helps,

Jan

Jan M. Knaup                      | Fon +49-(0)421-218-62351
Dipl. Phys. Dr. rer. nat.         | Fax +49-(0)421-218-62770
Universität Bremen - BCCMS        |
Am Fallturm 1                     | Jan.Knaup at bccms.uni-bremen.de
28359 Bremen                      | JanKnaup at gmail.com
Germany                           | www.bccms.uni-bremen.de


2012/7/11 R.Perez Garcia <r.perez.garcia at student.rug.nl>

> Dear dr. Penazzi,
> Thank you very much for your kind answer.
> I believe i follow the tutorial adecquately. I should copy the answer
> prof. Aradi gently send me a few seconds ago.
> " If you use MaxSCCIterations = 1, the SCC won't converge, but you also
> do not want it to converge, so it is fine.   Best regards,  Bálint"
> So that problem is solved. However now I have dificulties to plot the
> band_tot.dat if somebody could please explain the structure of the output
> would be fantastic.
> Thank you very much for your attention.
> Best regards: Rodrigo
>
>
>
> On 11-07-12, *Gabriele Penazzi * <gabriele.penazzi at bccms.uni-bremen.de>
> wrote:
>
>  On 07/11/2012 09:04 AM, R.Perez Garcia wrote:
>
>   Dear Prof. Aradi,
>
> Dear DFTB+ especialists,
>
>
>
>
> I am starting to use DBTB+ and I successfully did so until now.
> I can not calculate the band structure due to a convergence problem.
> I did follow your tutorial, and after SCC convergence (21iterations) and
> satisfactorily calculate the DOS, the BandStructure calculation crashes.
>
> I put the necessary files, charges.bin and geom.gen, in a new directory
> together with the dftb_in.hsd (with all the small changes suggested by you,
> I think ) but it can not converged.[cut]
>
>
> Hi Rodrigo,
>
> from your input file and output error it looks like you're trying to solve
> the SCC cycle again. This is wrong, you must first calculate the charge
> density with a k-point sampling suitable for that, and then import the
> charge in the band structure calculation WITHOUT solving the scc cycle
> again. Otherwise the code will try to  solve it using as a k-point sampling
> the k lines you specified, that's why it doesn't converge.
>
> Check the online example:
>
> http://www.dftb-plus.info/fileadmin/DFTB-Plus/public/recipes/html/basics/bandstruct.html
>
> In the section "Calculating the band structure" in the input file there's
> a flag "ReadInitialCharges = Yes"
> Copy again your charges from the converged calculation and use this flag
> (which gives instruction to the code not to calculate the charge again),
> and probably your problem will be gone.
>
> Gabriele
>
>
>
> --
> Dr. Gabriele Penazzi
> BCCMS - University of Bremen
> http://www.bccms.uni-bremen.de/http://sites.google.com/site/gabrielepenazzi/
>
> phone: +49 (0) 421 218 62337
> fax: +49 (0) 421 218 62770
>
>
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>
>
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