[Wien] BerryPI

[nilofar hadaeghi]

Dear all

I have studied the polarization of some metal and insulator cases using the
latest version of the berryPI code. We performed the scf calculations by
Wien2k14.2.  One of Our calculations for one of my cases using GGA method
show that this case is an insulator in agreement with experimental reports.
The structure of this compound is centrosymmetric in the Pm3m space group.

So based on the theoretical background of berryPI code it is expected that
the polarization value for this compound must be zero. After running the
code for this compound using this command

berrypi -k6:6:6

the results has been achieved as what was expected and copied below:

------------------------------------------------------------
---------------------------

Electronic polarization (C/m2)     sp(1)  [ 0.000000e+00,  0.000000e+00,
0.000000e+00]

Ionic polarization (C/m2)          sp(1)  [ 1.366237e-11,  1.366237e-11,
1.366237e-11]

Tot. spin polariz.=Pion+Pel (C/m2) sp(1)  [ 1.366237e-11,  1.366237e-11,
1.366237e-11]

------------------------------------------------------------
---------------------------

TOTAL POLARIZATION (C/m2)          both   [ 1.366237e-11,  1.366237e-11,
1.366237e-11]

------------------------------------------------------------
---------------------------

We also performed calculations for another case. We have used the GGA+U
(U>6eV) method for this case  to obtain the suitable gap compared to
experiment.  The GGA method leads to zero gap in contrast to experiment.
The same as previous studied case, this structure is centrosymmetric(space
group :Pm3m)



 So we expect the zero polarization vector for this compound too, but the
results show the non-zero polarization for the mentioned method in contrast
to theory. Could you help me to solve this problem, please?



In the GGA+U method and ferromagnetic polarization (with  SP calculation),
after running the command:

berrypi -o -k10:10:10

------------------------------------------------------------
---------------------------

Electronic polarization (C/m2)     sp(1)  [-5.253369e-01,  5.253369e-01,
-5.253369e-01]

Ionic polarization (C/m2)          sp(1)  [ 3.304038e-11,  3.304038e-11,
3.304038e-11]

Tot. spin polariz.=Pion+Pel (C/m2) sp(1)  [-5.253369e-01,  5.253369e-01,
-5.253369e-01]

------------------------------------------------------------
---------------------------

Electronic polarization (C/m2)     sp(2)  [ 0.000000e+00,  0.000000e+00,
0.000000e+00]

Ionic polarization (C/m2)          sp(2)  [-5.253369e-01, -5.253369e-01,
-5.253369e-01]

Tot. spin polariz.=Pion+Pel (C/m2) sp(2)  [-5.253369e-01, -5.253369e-01,
-5.253369e-01]

---------------------------------------------------------------------------------------
TOTAL POLARIZATION (C/m2)          both   [-1.050674e+00,  6.700285e-11,
-1.050674e+00]
======================================================================================

We also performed our calculations using the GGA method without spin
polarization. after running the command

 berrypi -k10:10:10

------------------------------------------------------------
---------------------------

Electronic polarization (C/m2)     sp(1)  [-1.470943e-01,
-9.456064e-02,  2.626685e-01]

Ionic polarization (C/m2)          sp(1)  [-5.253369e-01, -5.253369e-01,
-5.253369e-01]

Tot. spin polariz.=Pion+Pel (C/m2) sp(1)  [-6.724312e-01, -6.198976e-01,
-2.626685e-01]

------------------------------------------------------------
---------------------------

TOTAL POLARIZATION (C/m2)          both   [-6.724312e-01, -6.198976e-01,
-2.626685e-01]

------------------------------------------------------------
---------------------------
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