[Pw_forum] a problem with polarization

[Jess Kondor]

 Dear all,

I am working on bulk multiferroic, BiFeO3. It is suppose to have a
spontaneous polarization around 100 mC/cm^2 along [111] direction .
However, I got ~2.5 mC/cm^2 using LSDA+U approximation and Berry Phase
method:

along x:           P =   0.0143864  (mod   0.7250294)  C/m^2
along y:           P =   0.0143881  (mod   0.7250294)  C/m^2
along z:           P =   0.0139124  (mod   0.7250294)  C/m^2

P_[111]=sqrt(Px*Px + Py*Py + Pz*Pz) = 2.47 mC/cm^2 . The funny part is
that using the same structure and ABINIT code I was able to get a
value of polarization that is closed  to 100 mC/cm^2. I am sure that I
did something wrong and there is a simple explanation to this. All
other parameters (lattice parameters, wyckoff positions) obtained by
PWscf and ABINIT are almost equivalent.

 Does anybody have any hints?

Best regards,

--
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Jess Kondor,
 PhD student

PICYT, Av. Venustiano Carranza 2425-A,
San Luis Potosí 78210, México
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