[Pw_forum] Space Group Issue

[Paolo Giannozzi]

 I would try first of all to remove ibrav. If you specify a space group,
the code should find the proper value of "ibrav"

On Mon, Sep 18, 2017 at 5:25 PM, Amar Singh <amarsingh122014 at rediffmail.com>
wrote:

> Dear Friends,
> ​Its my first appearance on forum and hope I can reach you via
> pw_forum at pwscf.org.
>
> I am trying to optimize the structure of BaTiO3 in R3C space group (No.
> 161). I am using the lattice parameters as suggested on QE website, Celldm
> (1) = a (bohr) and Celldm (3) = c/a. While b = a and angles are 90, 90 and
> 120 (hexagonal setting) are fixed for the space group. Space group should
> be able to generate 30 atoms (6 BaTiO3 units) in the unit cell. Following
> is the part of script I am using.
>
> &system
>     ibrav =  4,
>     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
>
> As I start the run, I am encountered with the error message "ibrav not
> compatible with the space group number". If I look for other ibrav options (
> http://www.quantum-espresso.org/wp-content/uploads/Doc/
> INPUT_PW.html#CELL_PARAMETERS), I do not find any other having a and c/a
> as inputs (as they are the only independent lattice parameters for
> hexagonal setting of R3C space group !). Please suggest me what should I
> try, and if I am doing anything wrong !!
>
> 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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