[DFTB-Plus-User] band structure SCC convergence

[Gabriele Penazzi]

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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