[Wien] no effect of an external electric field on the splitting in graphene

[Peter Blaha]

Put R2V in case.in0 and plot the resulting potentials with lapw5.
(eventually as difference with-without efield).
You should clearly see how the efield is added.

Martin Gmitra schrieb:
> Dear Wien2k users,
> To move ahead I checked lapw0.F and xcpot3.F for corresponding parts
> including ramp potential to xc potential. There are some commented parts
> of the code. However, I am not expert, I would like to ask you if you can
> check whether some relevant parts should not be uncommented for proper
> including the ramp potential in lapw0. I am referring to Wien2k version 08.2
> and 08.3.
> Many thanks,
> Martin Gmitra
> 
> 
> On Tue, Sep 9, 2008 at 11:06 AM, Martin Gmitra 
> <martin.gmitra at physik.uni-regensburg.de 
> <mailto:martin.gmitra at physik.uni-regensburg.de>> wrote:
> 
>     Thank you for your answer. We prepared symmetry of the system 
>     in the same way as you are proposing. All the calculations have 
>     been performed using the following potential expansion in case.in2c:
> 
> 
> 
> 
>     TOT             (TOT,FOR,QTL,EFG,FERMI)
>           -9.0       8.0 0.50 0.05                EMIN, NE, ESEPERMIN, ESEPER0
>     TETRA    0.000          (GAUSS,ROOT,TEMP,TETRA,ALL      eval)
>       0 0  1 0  2 0  3 0  3 3  4 0  4 3  5 0  5 3  6 0  6 3  6 6
> 
> 
> 
>      20.00          GMAX
>     //
>     I think that the local symmetry we have used is OK. What do you think?
>     Best,
>     Martin Gmitra
> 
> 
> 
>     Most likely this is a "symmetry" problem.
> 
>     One cannot put the graphene sheet at an arbitrary z-position. Remember, 
> 
> 
> 
>     adding an E-field means that we change the Coulomb-potential.
>     In order to keep periodicity, we use a zig-zag potential and of course 
>     it does NOT make sense to put an atom at the position of the "kink"
> 
> 
> 
>     (z=0 or 0.5).
> 
>     Of course when one adds an E-field along the z-direction, the mirror
>     symmetry within the graphene plane has gone. Thus it is essential to 
>     have this fact reflected in the local symmetry (eg. you need a LM=1 0
> 
> 
> 
>     term for the E-field, which is normally absent for a single sheet).
> 
>     I'd recommend to setup the struct file with 2 graphene layers (at z=0 
>     and 0.25), but one should contain eg. B atoms instead of C. After 
> 
> 
> 
>     symmetry detection, remove the B-sheet (at z=0).
> 
>     Martin Gmitra schrieb:
>     >/ Dear Wien2k users,
>     />/ 
>     />/ We are running Wien2k 08.2 version on IBM AIX v 5.3 system (Uni Leoben). 
>     />/ We are interested in effects of an external
> 
> 
> 
>     />/ electric field on splitting in the graphene. We have recovered 24 micro 
>     />/ eV splitting due to intrinsic spin-orbit interaction
>     />/ in the K-point. Setting up a ramp potential of rather huge amplitudes 
> 
> 
> 
>     />/ (1000 Ry/20A) has no effect on the splitting at all.
>     />/ I have not found relevant discussion in mailing list. Therefore, I would 
>     />/ like to share my problem with you.
>     />/ 
> 
> 
> 
>     />/ The graphene sheet has been placed (i) in the quarter of the unit cell 
>     />/ width (z=0.25) and complex calculations have
>     />/ run and; (ii) the sheet has been positioned in the origin (z=0) and real 
> 
> 
> 
>     />/ calculations have run with modified ramp
>     />/ potential in eramps.f within lapw0. The results we have obtained are 
>     />/ almost the same - no change in the splitting.
>     />/ 
>     />/ My question is:
> 
> 
> 
>     />/ Is the present implementation of the external electric field suitable 
>     />/ for monoatomic slab structures including
>     />/ spin-orbit coupling interaction?
>     />/ 
>     />/ Many thanks,
> 
> 
> 
>     />/ Martin Gmitra/
> 
> 
> 
> ------------------------------------------------------------------------
> 
> _______________________________________________
> Wien mailing list
> Wien at zeus.theochem.tuwien.ac.at
> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien