[Pw_forum] tetrahedra and vc-relax

[Giuseppe Mattioli]

Dear Chiara
Thank you very much for the update! I was not aware yet of such new  
implementations and I was erroneously quoting from the 6.0 manual...
Best
Giuseppe

Quoting chiara.ricca at dcb.unibe.ch:

> Dear Dr. Kawamura thanks a lot for the patch.
>
>
> Dear Giuseppe,
>
> after discussion of our collaborators with Paolo Giannozzi and  
> Stefano De Gironcoli,
>
> we learned that it is possible in QE v 6.1 to use tetrahedra for  
> relax and vc-relax calculations for insulators/semiconductors,
>
> especially using the the  optimized tetrahedron method  
> (occupations='tetrahedra_opt'), as reported in the
>
> pw.x manual for version 6.1:
>
>  Available options are:
>
>
> 'smearing' :
>
> gaussian smearing for metals;
> see variables  
> smearing<http://www.quantum-espresso.org/wp-content/uploads/Doc/INPUT_PW.html#smearing> and  
> degauss<http://www.quantum-espresso.org/wp-content/uploads/Doc/INPUT_PW.html#degauss>
>
>
> 'tetrahedra' :
>
> Tetrahedron method, Bloechl's version:
> P.E. Bloechl, PRB 49, 16223  
> (1994)<https://journals.aps.org/prb/abstract/10.1103/PhysRevB.49.16223>
> Requires uniform grid of k-points, to be
> automatically generated (see card  
> K_POINTS<http://www.quantum-espresso.org/wp-content/uploads/Doc/INPUT_PW.html#K_POINTS>).
> Well suited for calculation of DOS,
> less so (because not variational) for
> force/optimization/dynamics calculations.
>
>
> 'tetrahedra_lin' :
>
> Original linear tetrahedron method.
> To be used only as a reference;
> the optimized tetrahedron method is more efficient.
>
>
> 'tetrahedra_opt' :
>
> Optimized tetrahedron method:
> see M. Kawamura, PRB 89, 094515  
> (2014)<https://journals.aps.org/prb/abstract/10.1103/PhysRevB.89.094515>.
> Can be used for phonon calculations as well.
>
>
> 'fixed' :
>
> for insulators with a gap
>
>
> 'from_input' :
>
> The occupation are read from input file,
> card  
> OCCUPATIONS<http://www.quantum-espresso.org/wp-content/uploads/Doc/INPUT_PW.html#OCCUPATIONS>. Option valid only for  
> a
> single k-point, requires  
> nbnd<http://www.quantum-espresso.org/wp-content/uploads/Doc/INPUT_PW.html#nbnd> to be  
> set
> in input. Occupations should be consistent
> with the value of  
> tot_charge<http://www.quantum-espresso.org/wp-content/uploads/Doc/INPUT_PW.html#tot_charge>.
>
>
>
> Best,
>
> Chiara
>
>
>
>
> ________________________________
> De : pw_forum-bounces at pwscf.org <pw_forum-bounces at pwscf.org> de la  
> part de Giuseppe Mattioli <giuseppe.mattioli at ism.cnr.it>
> Envoyé : mercredi 18 octobre 2017 10:48:15
> À : pw_forum at pwscf.org
> Objet : Re: [Pw_forum] tetrahedra and vc-relax
>
>
> Dear Chiara
> You should not use occupations='tetrahedra' for relax or vc-relax
> calculations! The reason is clearly stated in the pw.x manual. Use
> smearing instead
>
>
>     Variable:       occupations
>
>     Type:           CHARACTER
>     Description:
>                     Available options are:
>
>                     'smearing' :
>                          gaussian smearing for metals;
>                          see variables "smearing" and "degauss"
>
>                     'tetrahedra' :
>                          especially suited for calculation of DOS
>                          (see P.E. Bloechl, PRB 49, 16223 (1994)).
>                          Requires uniform grid of k-points,
>                          automatically generated (see below).
>                          Not suitable (because not variational) for
>                          force/optimization/dynamics calculations.
>
>                     'fixed' :
>                          for insulators with a gap
>
>                     'from_input' :
>                          The occupation are read from input file,
>                          card "OCCUPATIONS". Option valid only for a
>                          single k-point, requires "nbnd" to be set
>                          in input. Occupations should be consistent
>                          with the value of "tot_charge".
>
>
> HTH
> Giuseppe
>
> Quoting chiara.ricca at dcb.unibe.ch:
>
>> Dear all,
>>
>> I'm trying to perform a "vc-relax" calculation using the tetrahedron
>> method with QE v 6.1.
>>
>> The calculation stops after having printed the final geometry,
>> during the final scf step.
>>
>> It does not write any error and the scheduler only reports a
>> segmentation fault.
>>
>> I have tried with both tetrahedra and tetrahedra_opt, but I have the
>> same issue.
>>
>> The problem is not there if I do a "relax" calculation.
>>
>> Please find attached, the input and output of an example.
>>
>> Thanks in advance!
>>
>> Regards,
>>
>> Chiara Ricca
>>
>> ---
>>
>> Postdoctoral fellow
>>
>> University of Bern
>
>
>
> GIUSEPPE MATTIOLI
> CNR - ISTITUTO DI STRUTTURA DELLA MATERIA
> Via Salaria Km 29,300 - C.P. 10
> I-00015 - Monterotondo Scalo (RM)
> Mob (*preferred*) +39 373 7305625
> Tel + 39 06 90672342 - Fax +39 06 90672316
> E-mail: <giuseppe.mattioli at ism.cnr.it>
>
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GIUSEPPE MATTIOLI
CNR - ISTITUTO DI STRUTTURA DELLA MATERIA
Via Salaria Km 29,300 - C.P. 10
I-00015 - Monterotondo Scalo (RM)
Mob (*preferred*) +39 373 7305625
Tel + 39 06 90672342 - Fax +39 06 90672316
E-mail: <giuseppe.mattioli at ism.cnr.it>