[QE-users] Convergence issue of a 2x2x2 supercell with Ni (111) surface

[Suraj P]

Convergence issue of a 2x2x2 supercell with Ni (111) surface

Dear all,
My objective of using QE is to calculate the adsorption energy of diphenyl ether over Ni (111) surface.

Initially I have taken CIF file of FCC Ni and created a 2x2x2 supercell (7 layer) of Ni in VESTA.
Next I have transformed the (111) surface of this supercell, so as to expose the (111) surface to top of this supercell. 
Next I have added 10A vacuum in z direction.(After this the supercell was periodic in x and y direction but not in z direction). 


Next I have done a relaxation calculation where in Im facing the convergence problem. 
I have tried various pseudopotentials (PAW and ultrasoft), also I have tried with Cg and Davidson diagonilization. 
I have tried with ibrav =8 (Orthorhombic) and 14 (triclinic). 
Ecutwfc and Ecutrho were chosen from the pseudopotentiafile. However the convergence is not achieved in any case.

Kindly have a look into my input file and help me in troubleshooting this issue.

______________________________________________________________________________________________________________________________________________________

   &CONTROL
    calculation   = "relax"
    prefix= 'Ni222'
    tstress         = .true.
    tprnfor         = .true.
    verbosity       = 'high'
    etot_conv_thr   = 1e-6
    forc_conv_thr   = 1e-5
    pseudo_dir='./pseudo'
    outdir = './outdir'

/
&SYSTEM
    a     =  8.51233e+00
    b     =  4.91460e+00
    c     =  2.20383e+01
    ibrav = 8
    nat   = 56
    ntyp  = 1
    ecutwfc =45
    ecutrho =250
    noncolin =.true.
    lspinorb =.true.
    !nspin =2
    occupations ='smearing' 
     smearing ='gaussian'
     degauss =0.002
    starting_magnetization = 0.5
	
/
&ELECTRONS
    conv_thr         =  1.00000e-06
    mixing_beta      =  7.00000e-01
    startingpot      = "atomic"
    startingwfc      = "atomic+random"
/
&IONS
ion_positions='from_input'
ion_dynamics  = "bfgs"
/
&CELL  
/
ATOMIC_SPECIES
Ni     58.69340  Ni.pbe-spn-kjpaw_psl.1.0.0.UPF

ATOMIC_POSITIONS {angstrom}
Ni      0.000000   0.000000   0.000000
Ni      0.000000   0.000000  12.038267
Ni      5.674892   0.000000   8.025519
Ni      2.837442   0.000000   4.012748
Ni      2.837442   0.000000  10.031882
Ni      0.000000   0.000000   6.019134
Ni      5.674892   0.000000   2.006385
Ni      7.093609   2.457299  10.031882
Ni      4.256167   2.457299   6.019134
Ni      1.418725   2.457299   2.006385
Ni      1.418725   2.457299   8.025519
Ni      7.093609   2.457299   4.012748
Ni      4.256167   2.457299   0.000000
Ni      4.256167   2.457299  12.038267
Ni      0.709358   1.228650  10.031882
Ni      6.384250   1.228650   6.019134
Ni      3.546809   1.228650   2.006385
Ni      3.546809   1.228650   8.025519
Ni      0.709358   1.228650   4.012748
Ni      6.384250   1.228650   0.000000
Ni      6.384250   1.228650  12.038267
Ni      7.802976   3.685949   8.025519
Ni      4.965525   3.685949   4.012748
Ni      2.128084   3.685949   0.000000
Ni      2.128084   3.685949  12.038267
Ni      2.128084   3.685949   6.019134
Ni      7.802976   3.685949   2.006385
Ni      4.965525   3.685949  10.031882
Ni      0.709358   3.685949  10.031882
Ni      6.384250   3.685949   6.019134
Ni      3.546809   3.685949   2.006385
Ni      3.546809   3.685949   8.025519
Ni      0.709358   3.685949   4.012748
Ni      6.384250   3.685949   0.000000
Ni      6.384250   3.685949  12.038267
Ni      7.802976   1.228650   8.025519
Ni      4.965525   1.228650   4.012748
Ni      2.128084   1.228650   0.000000
Ni      2.128084   1.228650  12.038267
Ni      2.128084   1.228650   6.019134
Ni      7.802976   1.228650   2.006385
Ni      4.965525   1.228650  10.031882
Ni      7.093609   0.000000  10.031882
Ni      4.256167   0.000000   6.019134
Ni      1.418725   0.000000   2.006385
Ni      1.418725   0.000000   8.025519
Ni      7.093609   0.000000   4.012748
Ni      4.256167   0.000000   0.000000
Ni      4.256167   0.000000  12.038267
Ni      5.674892   2.457299   8.025519
Ni      2.837442   2.457299   4.012748
Ni      0.000000   2.457299   0.000000
Ni      0.000000   2.457299  12.038267
Ni      0.000000   2.457299   6.019134
Ni      5.674892   2.457299   2.006385
Ni      2.837442   2.457299  10.031882

K_POINTS {automatic}
 1  1  1  0 0 0
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  Thanking you
  Suraj
  Research student, IIT Kharagpur