[Pw_forum] Space Group Issue

[Amar Singh]

Thanks for the suggestion Paolo Giannozzi. ​Removing ibrav working fine partially. Space group 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.thanks​ASFrom: "Amar Singh"<amarsingh122014 at rediffmail.com>Sent: Mon, 18 Sep 2017 20:55:14To: <pw_forum at pwscf.org>Subject: Space Group IssueDear 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 = 161ATOMIC_POSITIONS crystal_sgBa 0.00000 0.00000 0.26640 1 1 1Ti 0.00000 0.00000 0.01568 1 1 1O 0.1338 0.3363 0.08333 1 1 1As 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 !!thanksAS
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