[QE-users] Structure with symmetry

[Paolo Giannozzi]

On Fri, Mar 19, 2021 at 11:05 AM Offermans Willem <willem.offermans at vito.be>
wrote:

The last line says: "Symmetry operations form a group”.
> Great, which group is it?
>

routine find_symmetry finds only symmetry operations and checkst that they
form a group. Which one, it is found later in a different routine. What you
prpose (printing the group name where the above message is issued) would
require some extensive changes.

Paolo


> 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
>
>
> On 18 Mar 2021, at 17:39, Lorenzo Paulatto <paulatz at gmail.com> wrote:
>
> Oddly enoughm the scan_ibrav.x little program does not work in your case
> (I'm fixing it), but cell2ibrav does:
> $ PW/tools/cell2ibrav.x
> Enter the lattice vectors (one per line)
> 1.000000   0.000000   0.000000
> 0.000000   1.500000   0.000000
> 0.000000   0.000000   4.596194
> Enter alat (or 'x' to skip if axis are in bohr)
> 10.627880
> ibrav =      8
> celldm(1) =     10.62788000
> celldm(2) =      1.50000000
> celldm(3) =      4.59619400
> New lattice vectors in bohr:
>    10.62788000     0.00000000     0.00000000
>     0.00000000    15.94182000     0.00000000
>     0.00000000     0.00000000    48.84779829
> New lattice vectors in old alat:
>     1.00000000     0.00000000     0.00000000
>     0.00000000     1.50000000     0.00000000
>     0.00000000     0.00000000     4.59619400
> New lattice vectors in new alat:
>     1.00000000     0.00000000     0.00000000
>     0.00000000     1.50000000     0.00000000
>     0.00000000     0.00000000     4.59619400
> Discrepancy old/new in bohr =     0.000000
>
> --
> Lorenzo Paulatto - Paris
> On Mar 18 2021, at 10:03 am, Offermans Willem <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
> <https://eur02.safelinks.protection.outlook.com/?url=https%3A%2F%2Flink.getmailspring.com%2Flink%2F2AD46120-DDAD-4F73-91B7-A26C8881CEA0%40getmailspring.com%2F0%3Fredirect%3Dmailto%253AWillem.Offermans%2540Vito.be%26recipient%3DdXNlcnNAbGlzdHMucXVhbnR1bS1lc3ByZXNzby5vcmc%253D&data=04%7C01%7C%7C0ede0550f7e64c0f1cb908d8ea2c6ed8%7C9e2777ed82374ab992782c144d6f6da3%7C0%7C1%7C637516823855682964%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=Lb1wEO%2FKzG2MuJSR0cu%2BfNjiZOLWaKOa%2F4i%2BkQ6528w%3D&reserved=0>
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>
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-- 
Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
Univ. Udine, via delle Scienze 206, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222
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