[QE-users] Finite electric field polarisation

[Mostafa Youssef]

Dear Terry,

The dipole results need post-processing. One needs to subtract n x
polarization quantum to obtain a meaningful polarization.  n is an
integer.

Consider a simple dielectric like MgO at zero field. pw.x may give you
different dipoles in all directions, although physically in all directions
the net dipoles are zero. If you post-process as I indicated above you get
zero dipole as it should.

A good starter on this topic is this paper:
https://www.sciencedirect.com/science/article/abs/pii/S0022459612003234
A free arXiv version of it is also available.



Mostafa
AUC
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