[Pw_forum] Bilayer graphene with an electric field applied

[Gabriele Sclauzero]

Dear Elje,

    since you are dealing with a slab geometry and you want to apply the 
field along the direction perpendicular to the surface, why don't you 
use the sawtooth potential (tefield=.TRUE. instead of lefield=.TRUE.) to 
generate the E field?

On 09/28/2010 10:41 PM, Elie Moujaes wrote:
> Dear all,
> I
> I am trying to get the band structure of graphene under the effect of 
> an electric field. The problem is that the result at the end is very 
> messy and jiggly. I repeated the calculations many times but I still 
> get the same result. I first performed a scf calculation without the 
> electric field followed by a scf calculation with an electric field 
> and then the band calculation.
>

Do you have some evidence that your "messy and jiggly" band structure is 
wrong? Are you sure that you are visualizing it in the correct way?


HTH


GS

>
> SCF with electric field
>
> &control
>
> prefix='bi elgraphene',
>
> calculation='scf',
>
> restart_mode='from_scratch',
>
> lelfield = .true.,
>
> pseudo_dir = '/espresso-4.2/pseudo/',
>
> outdir='/tmp/results_MOUJAES/'
>
> /
>
> &system
>
> ibrav= 4, celldm(1) =4.608737, celldm(3)=5.330410, nat=4, ntyp= 1,
>
> ecutwfc = 110.D0,occupations='smearing',smearing='methfessel-paxton', 
> degauss=0.01
>
> /
>
> &electrons
>
> conv_thr=1.D-10,
>
> mixing_mode='plain'
>
> efield_cart(1) = 0.0,
>
> efield_cart(2) = 0.0,
>
> efield_cart(3) = 0.001,
>
> startingwfc = 'random'
>
> /
>
> ATOMIC_SPECIES
>
> C 12.0107 C.pz-vbc.UPF
>
> ATOMIC_POSITIONS crystal
>
> C 0.000000 0.000000 0.000000
>
> C 0.000000 0.000000 0.257692
>
> C 0.333333 -0.33333 0.000000
>
> C -0.333333 0.33333 0.257692
>
> K_POINTS automatic
>
> 38 38 1 0 0 0
>
>
> I noticed that part of the bands calculation output had a problem with 
> the convergence of one of thh eigenavalues as some of the input looked 
> like:
>
> per-process dynamical memory: 30.2 Mb
>
> Band Structure Calculation
> Davidson diagonalization with overlap
> c_bands: 1 eigenvalues not converged
> c_bands: 1 eigenvalues not converged
> c_bands: 1 eigenvalues not converged
> c_bands: 1 eigenvalues not converged
> c_bands: 1 eigenvalues not converged
> c_bands: 1 eigenvalues not converged
> c_bands: 1 eigenvalues not converged
> c_bands: 1 eigenvalues not converged
> c_bands: 1 eigenvalues not converged
> c_bands: 1 eigenvalues not converged
> c_bands: 1 eigenvalues not converged
> c_bands: 1 eigenvalues not converged
> c_bands: 1 eigenvalues not converged
> c_bands: 1 eigenvalues not converged
> c_bands: 1 eigenvalues not converged
> c_bands: 1 eigenvalues not converged
> c_bands: 1 eigenvalues not converged
> c_bands: 1 eigenvalues not converged
> c_bands: 1 eigenvalues not converged
> c_bands: 1 eigenvalues not converged
> c_bands: 1 eigenvalues not converged
> c_bands: 1 eigenvalues not converged
>
> Please can anyone suggest me of what could have gone wrong...
>
> Thanks
>
> Elie Moujaes
>
> University of Nottingham
>
> NG7 2RD
>
> UK
>
>
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>    


-- 

Gabriele Sclauzero, EPFL SB ITP CSEA
PH H2 462, Station 3, CH-1015 Lausanne

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