[Pw_forum] convergence problem of graphene system under homogeneous finite-field.

[lan haiping]

Hi. Everyone.
  I am performing some test works on graphene system  with electric-enthalpy
approach which was developed by Umari & Souza,
to examine its dielectric properties.
 My calculation came to scf convergence problem when i applied E=0.001
a.u.that is perpendicular to the graphene plane, the total-energy of this
system oscillates up and down as shown below :
"
    total energy              =   -22.10984675 Ry
     total energy              =   -31.05580980 Ry
     total energy              =   -21.97194327 Ry
     total energy              =   -22.49028278 Ry
     total energy              =   -22.62216901 Ry
     total energy              =   -23.00354121 Ry
     total energy              =   -24.57862186 Ry
     total energy              =   -21.98569845 Ry
     total energy              =   -24.92584359 Ry
     total energy              =   -24.96325979 Ry
     total energy              =   -22.09410112 Ry
     total energy              =   -32.84912151 Ry
     total energy              =   -22.00923042 Ry
     total energy              =   -27.67266074 Ry
     total energy              =   -29.60728014 Ry
     total energy              =   -21.49630504 Ry
     total energy              =   -23.72936622 Ry
     total energy              =   -23.50209359 Ry
     total energy              =   -22.52577866 Ry

"

Would anyone please give me some suggestion or comments ,et al ?  My running
script is given below.



Best Wishes,

H.P

graphene.scf.efield2.in

"
   &control
    calculation='scf'
    restart_mode='restart',
    prefix='graphene-SL',
    gdir=3,
    nppstr=1,
    lelfield=.true.,
    nberrycyc=6
    pseudo_dir='/home/haiping/espresso-3.2/pseudo',
    outdir='/home/haiping/tmp'
 /
 &system
    ibrav= 4, celldm(1)=4.648726267482302,
    celldm(3)= 5,
    nat=  2, ntyp= 1,
    ecutwfc = 30.0, nosym=.true.
 /
 &electrons
    diagonalization='cg',
    conv_thr =  1.0d-8,
    mixing_beta = 0.01,
    startingwfc='random',
    efield=0.001,
 /
ATOMIC_SPECIES
 C  12.0107 C.pz-rrkjus.UPF
ATOMIC_POSITIONS
 C  0.0000  0.000000  0.0
 C  0.3333  0.666667  0.0
K_POINTS
 16
 0.0  0.0   0.0   1
 0.0  0.25  0.0   1
 0.0  0.50  0.0   1
 0.0  0.75  0.0   1
 0.25 0.0   0.0   1
 0.25 0.25  0.0   1
 0.25 0.50  0.0   1
 0.25 0.75  0.0   1
 0.50 0.0   0.0   1
 0.50 0.25  0.0   1
0.50 0.50  0.0   1
 0.50 0.75  0.0   1
 0.75 0.0   0.0   1
 0.75 0.25  0.0   1
 0.75 0.50  0.0   1
 0.75 0.75  0.0   1
"






-- 
Hai-Ping Lan
Department of Electronics ,
Peking University , Bejing, 100871
lanhaiping at gmail.com, hplan at pku.edu.cn
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