[Pw_forum] How to get the most reliable dos/pdos results

[Stefano de Gironcoli]

what information do you want to obtain ?
is the result you get stable (in the sense that does not change 
significantly) if you increase the number of k-points or vary degauss a 
bit ?
pdos are a (quite) arbitrary way of decomposing dos in atomic and 
angular contributions. don't overestimate their information content. 
don't believe in exact numbers, but try to get a feeling of the trends..
believe in the results to the extent they do not depend seriously on the 
details of the calculations.

hope this helps

stefano

donsity of state, projected densi
On 06/03/2012 04:37 PM, Peng Chen wrote:
> Dear Stefnao,
>
> Thanks for your reply. Energy convergence (to 0.002 Ry) tests with a series
> of ecutwfc, erho, degauss, kpoints parameters have been done (I am not sure
> if there are other convergence tests for DOS). The experimental result will
> be available later, I just want to make sure I am not doing something wrong
> with choosing parameters. Someone told me to compare with all-electron
>   calculation results. I actually did it with Exciting code, but it was
> running for two weeks and  a power outage occurred...
>
> On Sun, Jun 3, 2012 at 2:40 AM, Stefano Baroni<baroni at sissa.it>  wrote:
>
>> Dear Peng,
>>
>> I do not know nor anybody here (nor elsewhere) could. Suppose somebody
>> does and tells you "3". What use would you do of that info? Would you use
>> "3" and justify your choice by the advice of Mr. XXX as read on mailing
>> list YYY?
>>
>> The correct way to proceed is: 1) form an idea of the level of accuracy
>> you need; 2) perform a convergence test until your target accuracy is met;
>> 3) stop there and don't ask for more accuracy than you actually need,
>> unless you want to test a specific algorithm/code and your level of
>> understanding of it.
>>
>> Good luck!
>> SB
>>
>> On Jun 3, 2012, at 4:44 AM, Peng Chen wrote:
>>
>> Dear QE users,
>>
>> I tried several dos/pdos calculations with different parameters listed in
>> the table below. The  results are a little different.
>> I am not sure which result is more reliable when the experimental results
>> are not available.
>>
>>                                   scf
>>                           nscf
>> 1. dos/pdos      smearing (mv,degauss=0.01)                  tetrahedra
>> 2. dos/pdos      smearing (mv,degauss=0.01)              smearing
>> (mv,degauss=0.01)
>> 3.  dos               tetrahedra
>>         tetrahedra
>>       pdos             smearing (mv,degauss=0.01)              smearing
>> (mv,degauss=0.01)
>>
>>
>>
>> --
>>    Best Regards.
>>          Peng
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>>
>> ---
>> Stefano Baroni - SISSA&   DEMOCRITOS National Simulation Center - Trieste
>> http://stefano.baroni.me [+39] 040 3787 406 (tel) -528 (fax) /
>> stefanobaroni (skype)
>>
>> La morale est une logique de l'action comme la logique est une morale de
>> la pensée - Jean Piaget
>>
>>
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>
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>
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