[Pw_forum] DC & BEC

[Chengyang Li]

Dear Suza It seems like BaTiO3 is not a simple cubic structure, so you should not choose ibrav=1. Chengyang ----- Original Message -----
> From: "Suza W" <suza.rri at gmail.com>
> To: "PWSCF Forum" <pw_forum at pwscf.org>
> Sent: Wednesday, November 30, 2011 3:32:15 PM
> Subject: [Pw_forum] DC & BEC
> Dear All,
> Being an epitome of ferroelectric, BaTiO3 has extensively been
> studied using PWSCF. However,  unfortunately, with several
> standard available USPP, I encounter  following unphysical  results : 
>        
>      Dielectric constant in cartesian axis
>           (-8142842.391767483       0.000000000       0.000000000 )
>           (       0.000000000-8142842.391767481       0.000000000 )
>           (       0.000000000       0.000000000-8142842.391767476 )
>           Effective charges (d Force / dE) in cartesian axis
>            atom      1   Ba
>       Ex  (    -1136.43937        0.00000        0.00000 )
>       Ey  (        0.00000    -1136.43937        0.00000 )
>       Ez  (        0.00000        0.00000    -1136.43937 )
>            atom      2   Ti
>       Ex  (    -1874.03151        0.00000        0.00000 )
>       Ey  (        0.00000    -1874.03151        0.00000 )
>       Ez  (        0.00000        0.00000    -1874.03151 )
>            atom      3   O 
>       Ex  (      931.42284        0.00000        0.00000 )
>       Ey  (        0.00000     1067.39482        0.00000 )
>       Ez  (        0.00000        0.00000     1067.39482 )
>            atom      4   O 
>       Ex  (     1067.39482        0.00000        0.00000 )
>       Ey  (        0.00000      931.42284        0.00000 )
>       Ez  (        0.00000        0.00000     1067.39482 )
>            atom      5   O 
>       Ex  (     1067.39482        0.00000        0.00000 )
>       Ey  (        0.00000     1067.39482        0.00000 )
>       Ez  (        0.00000        0.00000      931.42284 )
> Any suggestion for correcting these errors will be highly
> appreciated. 
> Here goes the input file which renders such a blunder. 
>  &system
>     ibrav =  1,
>     celldm(1) = 7.5589,
>     nat = 5,
>     ntyp=3,
>     ecutwfc = 30.0,
>         ecutrho = 240.0,
>  /
>  &electrons
>     diagonalization = 'david'
>     conv_thr =  1.0d-9
>     mixing_beta = 0.7
>  /
>  &ions
>  /
>  &cell
>  /
> ATOMIC_SPECIES
>  Ba  137.327       Ba.pbe-nsp-van.UPF
>  Ti   47.867       Ti.pbe-sp-van_ak.UPF
>  O    15.9994      O.pbe-van_ak.UPF
> ATOMIC_POSITIONS (alat)
> Ba  0.0  0.0  0.0
> Ti  0.5  0.5  0.5
> O  0.0  0.5  0.5
> O  0.5  0.0  0.5
> O  0.5  0.5  0.0
> K_POINTS {automatic}
>  8 8 8  1 1 1
> Thanking you,
> Yours sincerely,
> Suza W
> PhD Student
> Department of Materials Science
> Bangalore
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