[Wien] why the oscilation appear when I use supercell

[Torsten Andersen]

Dear Mr. Qiao,

it is difficult to tell from the information you give, but two ideas:

1) You may get convergence later... have you tried to simply wait? I 
believe the constraint "-cc 0.0001" is stricter in the 3*3*1 supercell 
than in the original unitcell.

2) You may need to use up to 3*3*1 times more k-points than for the 
simple cell (to use the "same" k-points in the two cases), although I am 
not sure there should be a direct connection.

Best regards,
Torsten Andersen.

ybqiao at theory.issp.ac.cn wrote:
> Dear wien2k users,
>       I try to calculate the electronic structure of TaS2. The results
> are very good when i use the unitcell(including one Ta atom and two S
> atoms)as tructure file.But when i use the supercell (3*3*1
> including 39 atoms) in structure file ,oscilation appear the
> selfconsistent iterations.and do not reach a convergent (-cc 0.0001 same
> as using the unitcell).what is the problem? thank you !!!!
>                                                      your  sincerely
>                                                              Y.B.Qiao
> 
> 
> 
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-- 
Dr. Torsten Andersen        TA-web: http://deep.at/myspace/
AG Hübner, Department of Physics, Kaiserslautern University
http://cmt.physik.uni-kl.de    http://www.physik.uni-kl.de/