[Pw_forum] Bismuth Titanate Structure

[Giovanni Cantele]

Let' consider the Bi atoms:
Bi             3.65032726386637    3.65032726386637    4.24815040995715
Bi             3.65032726386637    3.65032726386637   13.30504053709336
Bi             0.00000000000000    0.00000000000000   18.15341923828743
Bi             0.00000000000000    0.00000000000000   27.21030936542364
Bi             0.00000000000000    0.00000000000000   35.70661018533794
Bi             0.00000000000000    0.00000000000000   44.76350031247415
Bi             3.65032726386637    3.65032726386637      49.61187901366822
Bi             3.65032726386637    3.65032726386637      58.66876914080443

which I label from 1 to 8.

Now, you chose ibrav=7 which corresponds to a Tetragonal I (bct) whose 
lattice vectors are chosen, within QE,
as ( see Doc/INPUT_PW* ):

body centered tetragonal (i)
                   ================================
                      v1 = (a/2)(1,-1,c/a),  v2 = (a/2)(1,1,c/a),  v3 = 
(a/2)(-1,-1,c/a)

If we do explicitly write these vectors in bohr we get:
v1=  (  3.6503, -3.6503, 31.458 )
v2 = (  3.6503,  3.6503, 31.458 )
v3 = ( -3.6503, -3.6503, 31.458 )

Now, let's consider the
Bi             0.00000000000000    0.00000000000000   35.70661018533794
and add to it a crystal translation, in particular -v3. We get the new 
(equivalent) position
( 3.6503, 3.6503, 35.7066-31.458) = ( 3.6503, 3.6503, 4.2486)
which is exactly the same as the position of the first atom.

Therefore, (unless I did something wrong!) either you chose a wrong 
ibrav, or you specified wrong units, or you gave in input wrong atomic 
coordinates.

Also consider that your input file setting:
ecutwfc = 60.0,ecutrho=200,
is wrong because ecutrho = N * ecutwfc where N=4 if you use only norm 
conserving PPs, while N>4 if your calc. included US
PPs (as in your case).

Hope this helps,

    Giovanni

dev sharma wrote:
> Dear Sir,
>  Please tell how to resolve this problems as i am sure about the 
> position of atoms.. My a, b, c are also in Angstrom. Secondly, when i 
> am running the same file through PWGui, it is giving error---- wrong 
> number of columns.How to proceed further.
>
> Thanks
>
> On Fri, Jul 17, 2009 at 4:26 PM, Paolo Giannozzi 
> <giannozz at democritos.it <mailto:giannozz at democritos.it>> wrote:
>
>
>     On Jul 17, 2009, at 12:36 , dev sharma wrote:
>
>     > The output structure in XCRYSden window is seemed to be right
>
>     but it isn't. The messages below mean one thing: your data is
>     wrong. Remember that a,b,c are in ANGSTROM, and that the
>     lattice vectors are those described in the documentation and
>     reprinted on output (i.e. not necessarily the axis you like)
>
>     > WARNING: Atom 1 and atom 12 are very close !!!
>     >          Atom 12 deleted !!!
>     > WARNING: Atom 2 and atom 122 are very close !!!
>     >          Atom 122 deleted !!!
>     > WARNING: Atom 3 and atom 14 are very close !!!
>     >          Atom 14 deleted !!!
>     > WARNING: Atom 4 and atom 123 are very close !!!
>     >          Atom 123 deleted !!!
>     > WARNING: Atom 5 and atom 16 are very close !!!
>     >          Atom 16 deleted !!!
>     > WARNING: Atom 6 and atom 124 are very close !!!
>     >          Atom 124 deleted !!!......
>
>
>     Paolo
>     ---
>     Paolo Giannozzi, Dept of Physics, University of Udine
>     via delle Scienze 208, 33100 Udine, Italy
>     Phone +39-0432-558216, fax +39-0432-558222
>
>
>
>     _______________________________________________
>     Pw_forum mailing list
>     Pw_forum at pwscf.org <mailto:Pw_forum at pwscf.org>
>     http://www.democritos.it/mailman/listinfo/pw_forum
>
>
> ------------------------------------------------------------------------
>
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://www.democritos.it/mailman/listinfo/pw_forum
>   


-- 



Dr. Giovanni Cantele
Coherentia CNR-INFM and Dipartimento di Scienze Fisiche
Universita' di Napoli "Federico II"
Complesso Universitario di Monte S. Angelo - Ed. 6
Via Cintia, I-80126, Napoli, Italy
Phone: +39 081 676910
Fax:   +39 081 676346
E-mail: giovanni.cantele at cnr.it
        giovanni.cantele at na.infn.it
Web: http://people.na.infn.it/~cantele
Research Group: http://www.nanomat.unina.it
Skype contact: giocan74