I have a problem to interpret the direction of berry phase polarization. For instance, the results from my calculation of
BiGaO3 polarization (using Berry phase) which is show below
##########################################################################################
Polarization in cartesian coordinates (C/m^2):
(the sum of the electronic and ionic Berry phase has been fold into [-1, 1])
Electronic berry phase: -0.939401884E+00 -0.939401884E+00 -0.515854041E+00
Expectation value (PAW only): 0.000000000E+00 0.000000000E+00 -0.712449245E-02
Ionic: 0.469700971E+00 0.469700971E+00 0.809214786E+00
Total: -0.469700913E+00 -0.469700913E+00 0.286236253E+00
(I use ABINIT-6.6.3 with PAW my input code is attached below)
BiGaO3_polarization.in- my input
- (3.08 KiB) Downloaded 224 times
##########################################################################################
If i understand truly, the calculated polarization is 0.469700913 C/m^2 along -x direction, which is inconsistent with reference value http://pubs.acs.org/doi/abs/10.1021/cm0480418 that reported 1.519 C/m^2 (i am not sure about it's direction).
The ref. value is larger than 1 which may be fold in to [-1,1] (By ABINIT in my calculation) and then becomes about -0.469700913 C/m^2.
Therefore, my question is "How can I know the total polarization is really in [-1,1] or implicitly in [-1,1] due to it has been fold into" .
Or, if there is the way that can tell ABINIT to unfold the polarization (into [-1, 1]) and let it to be the real value, please advise me.
I am apologize if this is my misunderstand.
Any help and comment must be very appreciated.
Sittichain Pramchu
Ph.D. student, Applied Physics,
Department of Physics and materials science,
Faculty of science, Chiang Mai University,
Thailand