I am willing to set up a set of simple SCF calculations of thin films under constant external electric field.
As a warm-up exercise, I try to reproduce the various band structure topologies of graphene under perpendicular electric field, including the effect of SOC.

To do so, I added the following <fields> tag in the calculationSetup section:
<fields zsigma="0.0" sig_b_1="0.05" sig_b_2="-0.05" autocomp="T"
dirichlet="F" eV="F">
</fields>


But the calculation ends with the error message:
***************ERROR***************
B-fields can only be used in spin-polarized calculations
***************ERROR***************

Could someone help me to figure out what I am doing wrong?
Thanks in advance,

Simon


NOTE:
This is FLEUR version: fleur 35
Its git version is:
described by: MaX-R6.0-3-g5518b73

Dear all,

eventually, setting up a spin-polarized calculation solves the problem. I attach the resulting band-structure.
The disadvantage of this approach is that I had to impose a spin-polarized occupation for the carbon atoms in the inp.xml. While self-consistency brings the system towards a non-magnetic solution, the final net magnetic moment is not exactly zero but of the order of 8x10-7...

Parsing the output file, I still have one little question. Equal and opposite charges have been placed on the external sheets 1 and 2. Why does the code reports external electric fields of opposite magnitude on these two planes?

------------------------------------------------------------
parameters for external electric field:
total electronic charge = 12.00000
total nuclear charge = 12.00000
z-z1 of external sheet = 0.00000 a0 = 0.00000 A
charge on external sheet 1 = 0.00500 (surface density= 0.00027 e/a.u.**2)
external field on sheet 1 = -0.17264E+08 V/cm
charge on external sheet 2 = -0.00500 (surface density= -0.00027 e/a.u.**2)
external field on sheet 2 = 0.17264E+08 V/cm
NOTE: The equation for the E field assumes two oppositely charged plates.
You may need to divide by two before summing the external fields to avoid double counting
------------------------------------------------------------

I guess that in this case, the actual field within the capacitor is of 0.17264E+08 V/cm, which is consistent with the computed band-structure. Is that right?

Best regards,

Simon

I keep reporting this error, have you encountered it? If so, how to solve it

**************juDFT-Error*****************
Error message: z-mirror/inversion symmetry but second e-fieldsheet specified
Error occurred in subroutine: efield
Error from PE:0/1
*****************************************
Last known location:
Last timer:Initialization
Timerstack:
Timer:Total Run
*****************************************