[Pw_forum] Bilayer graphene with an electric field applied

[Elie Moujaes]

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.

 

SCF with no 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) = 0.0,
    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  
 

 

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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