[QE-users] Finite electric field polarisation

[Terry Frankcombe]

Hi folks

I am trying to perform some finite field calculations on a
moderate-sized cell (~1000 Ang^3), using PW example 10 as a guide.

When doing a zero field calculation (all efield_cart zero) the total
energy converges happily to whatever level I want (e.g. conv_thr=1.d-9).
However, the "Electronic Dipole on Cartesian axes" does not converge.
For all three axes I get numbers ranging approximately +/- 15, which
charge apparently randomly through this range as the iterations proceed.

The behaviour is essentially unchanged if I put the field on, with say
efield_cart(3)=0.001.

I think this is not what should happen.  Anyone have any
ideas/experience with fixing this?

(FWIW, this is a TM oxide with PBE+U, QE 6.6.)

Ciao
Terry