[QE-users] Structure with symmetry

Thu Mar 18 15:22:44 CET 2021

maybe you could provide the input file for further check
Giovanni

> On 18 Mar 2021, at 14:34, Offermans Willem <willem.offermans at vito.be> wrote:
> 
> Hi Giovanni and Quantum Espresso friends,
> 
> 
> Thank you for your response. It is very much appreciated.
> 
> You are right, by specifying the unit cell in the following
> way, the warning message disappeared.
> 
> <snip>
> ...
>    ibrav            = 8
>    celldm(1)        = 10.6279
>    celldm(2)        = 1.5
>    celldm(3)        = 4.5961940777125589086
> …
> </snip>
> 
> Though, I specified the cell dimensions in Bohr units, but this is 
> just a detail for this communication.
> 
> As bonus, I can now find the following in the output:
> 
> <snip>
> ...
>      point group C_i (-1)   
>      there are  2 classes
>      the character table:
> 
>        E     i    
> A_g    1.00  1.00
> A_u    1.00 -1.00
> 
>      the symmetry operations in each class and the name of the first element:
> 
>      E        1
>           identity                                               
>      i        2
>           inversion                                          
> …
> </snip>
> 
> I wonder whether this is compatible to the following output, obtained in the old fashioned way.
> 
> <snip>
> ...
>     Found symmetry operation: I + ( -0.5000  0.0000 -0.0000)
>      This is a supercell, fractional translations are disabled
>      Message from routine find_sym:
>      Not a group! Trying with lower acceptance parameter...
>      Message from routine find_sym:
>      Symmetry operations form a group
> …
> </snip>
> 
> The last line says: "Symmetry operations form a group”.
> Great, which group is it?
> 
> 
> 
> Met vriendelijke groeten,
> Mit freundlichen Grüßen,
> With kind regards,
> 
> 
> Willem Offermans
> Researcher Electrocatalysis SCT
> VITO NV | Boeretang 200 | 2400 Mol
> Phone:+32(0)14335263 Mobile:+32(0)492182073 
> 
> Willem.Offermans at Vito.be <mailto:Willem.Offermans at Vito.be>
> <vito.jpg>
> 
>> On 18 Mar 2021, at 10:13, Giovanni Cantele <giovanni.cantele at spin.cnr.it <mailto:giovanni.cantele at spin.cnr.it>> wrote:
>> 
>> Here, a list of the ibrav values that you can choose
>> https://www.quantum-espresso.org/Doc/INPUT_PW.html#idm200 <https://eur02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.quantum-espresso.org%2FDoc%2FINPUT_PW.html%23idm200&data=04%7C01%7C%7C7db3d1168d674e9bc47b08d8e9ee7e1a%7C9e2777ed82374ab992782c144d6f6da3%7C0%7C1%7C637516557853981073%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=6NM1WCXt2ogavB5wbKfDwv1wmeybmvhrmyyh2PPpEnM%3D&reserved=0>
>> 
>> It seems that you have a simple orthorhombic lattice, that should correspond to ibrav = 8.
>> Than you can specify the variables
>> a
>> b
>> c
>> as crystal axes lengths in Angstrom units.
>> 
>> Giovanni
>> 
>> 
>>> On 18 Mar 2021, at 10:03, Offermans Willem <willem.offermans at vito.be <mailto:willem.offermans at vito.be>> wrote:
>>> 
>>> 
>>> Dear Quantum Espresso friends,
>>> 
>>> In most of my calculations, I’m dealing with metallic slabs, representing
>>> surfaces, derived from fcc metals, such as (221) or (533).
>>> 
>>> In these calculations, I’m dealing with structures with symmetry.
>>> The single symmetry element is an inversion center. S_2 is the Schönfließ symbol,
>>> if I recall correctly. 
>>> 
>>> In the output file of pw.x, I encounter the following note:
>>> 
>>> <snip>
>>> ...
>>>      Message from routine setup:
>>>      using ibrav=0 with symmetry is DISCOURAGED, use correct ibrav instead
>>> …
>>> </snip>
>>> 
>>> The unitcell is defined as:
>>> 
>>> <snip>
>>> ...
>>>      celldm(1)=  10.627880  celldm(2)=   0.000000  celldm(3)=   0.000000
>>>      celldm(4)=   0.000000  celldm(5)=   0.000000  celldm(6)=   0.000000
>>> 
>>>      crystal axes: (cart. coord. in units of alat)
>>>                a(1) = (   1.000000   0.000000   0.000000 )  
>>>                a(2) = (   0.000000   1.500000   0.000000 )  
>>>                a(3) = (   0.000000   0.000000   4.596194 )  
>>> …
>>> </snip>
>>> 
>>> I would like to follow the advice to use the correct ibrav, but I need some help
>>> to determine the correct ibrav. 
>>> 
>>> Can someone help me to determine the correct Ibrav?
>>> 
>>> 
>>> 
>>> 
>>> 
>>> Met vriendelijke groeten,
>>> Mit freundlichen Grüßen,
>>> With kind regards,
>>> 
>>> 
>>> Willem Offermans
>>> Researcher Electrocatalysis SCT
>>> VITO NV | Boeretang 200 | 2400 Mol
>>> Phone:+32(0)14335263 Mobile:+32(0)492182073 
>>> 
>>> Willem.Offermans at Vito.be <mailto:Willem.Offermans at Vito.be>
>>> <vito.jpg>
>>> 
>>> _______________________________________________
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>> -- 
>> 
>> Giovanni Cantele, PhD
>> CNR-SPIN
>> c/o Dipartimento di Fisica
>> Universita' di Napoli "Federico II"
>> Complesso Universitario M. S. Angelo - Ed. 6
>> Via Cintia, I-80126, Napoli, Italy
>> e-mail: giovanni.cantele at spin.cnr.it <mailto:giovanni.cantele at spin.cnr.it>
>> Phone: +39 081 676910
>> Skype contact: giocan74
>> 
>> ResearcherID: http://www.researcherid.com/rid/A-1951-2009 <http://www.researcherid.com/rid/A-1951-2009>
>> Web page: https://sites.google.com/view/giovanni-cantele/home <https://eur02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fsites.google.com%2Fview%2Fgiovanni-cantele%2Fhome&data=04%7C01%7C%7C7db3d1168d674e9bc47b08d8e9ee7e1a%7C9e2777ed82374ab992782c144d6f6da3%7C0%7C1%7C637516557853991067%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=3LwrKsdaE9ol%2BicjrppzmUrVfumjyQ%2BOw%2Bm%2FAd2fIMo%3D&reserved=0>
>> _______________________________________________
>> Quantum ESPRESSO is supported by MaX (www.max-centre.eu <http://www.max-centre.eu/>)
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-- 

Giovanni Cantele, PhD
CNR-SPIN
c/o Dipartimento di Fisica
Universita' di Napoli "Federico II"
Complesso Universitario M. S. Angelo - Ed. 6
Via Cintia, I-80126, Napoli, Italy
e-mail: giovanni.cantele at spin.cnr.it
Phone: +39 081 676910
Skype contact: giocan74

ResearcherID: http://www.researcherid.com/rid/A-1951-2009
Web page: https://sites.google.com/view/giovanni-cantele/home

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