[Pw_forum] (really silly) questions about DOS calculations

[Stefano de Gironcoli]

Dear Eduardo Ariel Menendez

Please notice that Fermi-Dirac  approximation to delta function is 
obtained with nagauss=-99 (minus 99 )
If you specify ngauss=+99 you get a very wierd function which is a 
gaussian multiplied by some Hermite polynomial of degree 99*2 wildly 
oscillating with 99*2-1 zeros  within a few degauss around the fermi 
energy ...

We should disable use of degauss larger than 1 (or maybe 2).... and 
repalce ngauss in input with some more mnemonic definition as it is done 
in pw.x

best regards,
Stefano de Gironcoli

Eduardo Ariel Menendez P wrote:

>Thank you very much, Paolo.
>
>The problem is only with dos.x, and it arises with this input
>
>&inputpp
> outdir='/home/emenendez/MyPWSCF/Ti3SiC2/DOS/',
> prefix='tisic',
> fildos='tisic.dos',
> ngauss=99,
> degauss=0.01,
> Emin=0, Emax=25.0, DeltaE=0.1
>/
>
>If ngauss is set to 0,1 or -1, the DOS is calculated. The problem is
>independent of the options used for the nscf calculation (occupation,
>smearing,degauss)
>
>Best regards
>Eduardo
>  
>
>>On Sunday 23 January 2005 04:44, Eduardo Ariel Menendez P wrote:
>>
>>    
>>
>>>2) Can one use occupations='smearing'+degauss+smearing='fermi-dirac'
>>>for a DOS calculation? if yes, has someone met the '1.0E+193' problem?
>>>      
>>>
>>I never tried with fermi-dirac smearing, but it used to work with
>>simple gaussian smearing. Does the problem occur only with
>>fermi-dirac smearing or also with other kinds of smearing (simple
>>gaussian for instance)?
>>
>>Paolo
>>
>>    
>>
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