[Pw_forum] Space Group Issue

[Paolo Giannozzi]

If you give positions with respect to hexagonal axis, you need to set
"rhombohedral=.false.". In this way you obtain 2 Ba, 2 Ti, 6 O, which is
correct for the rhombohedral (also known as trigonal) cell.

Note that the celldm parameters (or A and C) should be those for the
rhombohedral latttice, not for the hexagonal one.



On Tue, Sep 19, 2017 at 8:16 AM, Amar Singh <amarsingh122014 at rediffmail.com>
wrote:

> Thanks for the suggestion *Paolo Giannozzi. *
> ​Removing ibrav working fine partially. Space group R3C (no. 161) itself
> generated six equivalent positions for Ba and Ti, which is correct
> according to the known structure. Though, even generated O atoms are six in
> numbers, which should be 18.
> ​I also confirmed the positions of all atoms by another software (Diamond)
> and it is able to generate 18 O atoms along with six Ba & Ti. Would be
> thankful for any suggestion on that.
> Following the section of script I am using.
>
>      &system
>     celldm(1) = 10.578,
>     celldm(3) = 2.475,
>     nat =  3,
>     ntyp = 3,
>     ecutwfc = 40
>     space_group = 161
>
> ATOMIC_POSITIONS crystal_sg
> Ba 0.00000 0.00000 0.26640 1 1 1
> Ti 0.00000 0.00000 0.01568 1 1 1
> O 0.1338 0.3363 0.08333 1 1 1
>
> thanks
> ​AS
>
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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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