[QE-users] Wyckoff site 8f missing from group 15

[Giovani Rech]

Dear Paolo,

Thank you very much for your feedback. I just realized that there was an error in my input file and after I’ve fixed it the structure is generated just as expected. The generation of Wyckoff positions are working perfectly.

Best regards,

Giovani Rech

> On 14 Apr 2019, at 17:00, Paolo Giannozzi <p.giannozzi at gmail.com> wrote:
> 
> Wyckoff positions that can be generated by (x,y,z) are never explicitly listed; the code recognizes that tau was not set to anything, sets it to (x,y,z). Could you please provide the input that doesn't work and the one that does?
> 
> Paolo
> 
>> On Sun, Apr 14, 2019 at 5:33 PM Giovani Rech <gio.pi.rech at gmail.com> wrote:
> 
>> 
>> I’ve been trying to construct a crystalline structure of symmetry C2/c, unique axis b, space group 15. The atoms lie in the 8f Wyckoff positions (http://www.cryst.ehu.es/cgi-bin/cryst/programs/nph-wp-list?gnum=15&gua=b). I tried using 
>> 
>>> Space_group = 15
>>> Uniqueb = .true. 
>> 
>> And assigning the atoms sites as instructed by the manual
>> 
>>> ATOMIC_POSITIONS crystal_sg
>>> F 8f  0.285000000    0.31700000    0.099700000
>> 
>> However, the programs fails and can’t find the Wyckoff site to generate the entire structure for this symmetry. In fact, when inspecting the wypos.f90 module (around line 1048) I noticed that this site specifically was not implemented, so if anyone else is facing the same problem, this might be cause. 
>> 
>> I believe that the problem could be corrected by adding
>> 
>>> ELSEIF (TRIM(wp)=='8f') THEN
>>>        tau(1)=inp(1)
>>>        tau(2)=inp(2)
>>>        tau(3)=inp(3)
>> 
>> In the wypos_15 subroutine (but I’m not sure, correct me if I’m wrong). For the time being, I circumvented the problem by using ibrav=-12 and explicitly assigning each atomic position.
>> 
>> Best regards,
>> 
>> Giovani Rech
>> Universidade de Caxias do Sul
>> Caxias do Sul - RS, Brasil 
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> 
> 
> -- 
> Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
> Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
> Phone +39-0432-558216, fax +39-0432-558222
> 
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