[Pw_forum] problems with integrated charge

[Vivek Ranjan]

thnx for your suggestions. i have yet to work it out. i agree that the
problem occurs when the system consists of large number of atoms. i do not
think its because of the bad data (if bad data means wrong initial
geometry). i have checked geometry in xcrysden. i have also encountered
these problems several times and often changing some parameters may make
the programme work, but i have not been able to come to a systematic
analysis of why it happens. its mostly trial and error.

thnx anyways,
vivek


> Paolo Giannozzi wrote:
>>
>> On Oct 25, 2006, at 24:22 , Vivek Ranjan wrote:
>>
>>> I am trying to relax a structure. Within 3 scf steps the program aborts
>>> with the following :
>>>
>>> WARNING: integrated charge= 207.40294106, expected= 208.00000000
>>>
>>> from electrons : error # 1
>>> charge is wrong
>>> [...]
>>> What could be the reason ?
>>
>> incorrect data. The only reason related to the code I am aware of, is
>> a failure of the parallel algorithm for subspace diagonalization. You
>> can try to disable it, following the instructions I posted a few days
>> ago.
> I often get this error message when parallel algorithm for subspace
> diagonalization
> is used for large supercell ( especially when celldm(3) is big for
> tetragonal cell )
> calculations. For the same system with smaller super cell, there is no
> such problem
> when a serial algorithm is used. So I think this is due to parallel
> algorithm in the
> code not the bad data.
>
> To let program continue running without this error message, I changed the
> line in PW/electron.90 " ABS( charge - nelec ) / charge > *1.0D-3* " to
> " ABS( charge - nelec ) / charge > *1.d0* ". When scf calculation is
> close to
> convergence, such WARNING message will disappear. I don't know if this is
> a good way to do. If yes, then criterion for relative charge difference
> is too
> strict and we need to change it. If not, as Paolo suggested, maybe we need
> to disable the parallel algorithm for subspace diagonalization.
>
> Liping
>
>> If you have evidence that your data is good and the code still doesn't
>> work, please provide a test
>>
>> Paolo
>>
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Vivek Ranjan                             Email : vranjan at chips.ncsu.edu
Center for High Performance Simulation   %