[QE-users] Out of plane electric field in polar slab calculation

[Johan Claudius Jean-Paul Félisaz]

Hi everyone,


I am trying to compute the dipole moment in a slab, subject to an external out of plane electric field.

>From what I understand, there are two main ways of dealing with slabs:

- the dipole correction, which also allows to compute the dipole moment directly.

- the truncated Coulomb potential with assume_isolated=2d


However, I have problems with both of these methods.


For the dipole correction, it is claimed in "Density functional perturbation theory for gated two-dimensional heterostructures" (the assume_isolated=2d paper), that linear response has not been developped for dipole correction. Does it mean that ionic relaxation is wrong with dipole correction ?


For the truncated Coulomb potential, I do not understand how to set the electric field. I would guess one must not use "tefield", because it is a seesaw potential, while the truncated potential requires a proper potential. I would then like to use "lelfield", but I feel like this is a whole other framework as well, not designed for slabs but for bulk systems.


So what is the standard for polar slabs with out of plane electric fields, to conduct both ionic relaxation, and dipole moment calculation ?


Thanks in advance,


Best regards,


Johan Félisaz
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