Berry Phase: Calculate the Polarization from "Born effective charge" or "Total dipole moment"?
Posted: Thu Jan 16, 2014 12:59 pm
Dear VASP users and Experts,
Once, after Berry Phase type calculation in VASP 5.2, I have got "Total Dipole Moment" of the system in "elec-Angs" unit. (Only c-axis parallel is interested for the moment.)
The first question to be asked: Do I need to divide this quantity with the number of ions (say, B) those are displaced along c-axis? (Because, I had to use 2x2x2 supercell to get insulating C-AFM ground state model based on spin-arrangement of B sites, using GGA.)
Second question: In my point, to get the "Polarization" value, I do divide the "Total Dipole Moment" by "Cell Volume" and multiply "One Electronic Charge" i.e. 1.6x10^(-19)C, and get "Polarization" in "μC/cm^2" unit. Do you think it is okay? OR........
I should divide the "Born Effective Charge" by "Area" perpendicular to the c-axis and so on maths for unit change into "μC/cm^2" ? (In my case it should be ab-plane.)
Thank you very much for your comments,
Tilak
<span class='smallblacktext'>[ Edited ]</span>
Once, after Berry Phase type calculation in VASP 5.2, I have got "Total Dipole Moment" of the system in "elec-Angs" unit. (Only c-axis parallel is interested for the moment.)
The first question to be asked: Do I need to divide this quantity with the number of ions (say, B) those are displaced along c-axis? (Because, I had to use 2x2x2 supercell to get insulating C-AFM ground state model based on spin-arrangement of B sites, using GGA.)
Second question: In my point, to get the "Polarization" value, I do divide the "Total Dipole Moment" by "Cell Volume" and multiply "One Electronic Charge" i.e. 1.6x10^(-19)C, and get "Polarization" in "μC/cm^2" unit. Do you think it is okay? OR........
I should divide the "Born Effective Charge" by "Area" perpendicular to the c-axis and so on maths for unit change into "μC/cm^2" ? (In my case it should be ab-plane.)
Thank you very much for your comments,
Tilak
<span class='smallblacktext'>[ Edited ]</span>