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Ni 100 surface relaxation

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Task

Relaxation of the first two layers of a Ni (100) surface.

Input

POSCAR

fcc (100) surface
 3.53
   .50000   .50000   .00000
  -.50000   .50000   .00000
   .00000   .00000  5.00000
  5
Selective Dynamics
Kartesisch
   .00000   .00000   .00000 F F F
   .00000   .50000   .50000 F F F
   .00000   .00000  1.00000 F F F
   .00000   .50000  1.50000 T T T
   .00000   .00000  2.00000 T T T
  • Ni lattice constant of 3.53 .
  • 1 atom per layer: p(1x1) cell.
  • 5 nickel layers.
  • First two layers (of one side) relaxed.
  • vacuum.

INCAR

  ISTART = 0; ICHARG = 2
    
general:
  SYSTEM = clean Ni(100) surface
  ENCUT = 270 
  ISMEAR = 2 ; SIGMA = 0.2
  ALGO = Fast
  EDIFF = 1E-6
    
spin:
  ISPIN=2
  MAGMOM = 5*1
    
dynamic:
  NSW = 100
  POTIM = 0.8
  IBRION = 1
  • Initial charge-density in startjob from overlapping atoms.
  • Default energy cut-off of 270 eV.
  • MP-smearing (metal).
  • Spin-polarized calculation with initial moment of 1.
  • Ionic relaxation used.

KPOINTS

k-points
0
Monkhorst-Pack
9 9 1
0 0 0
  • Equally spaced mesh.
  • Odd mesh, centered on .
  • 15 k points in irreducible Brillouin zone (IBZ).
  • Only one k point in z-direction for surface.

Calculation

  • The sample output for the forces in the OUTCAR file should look like this (first and last step):

First step:

POSITION                                       TOTAL-FORCE  (eV/Angst)
-----------------------------------------------------------------------------------
     0.00000      0.00000      0.00000         0.000000      0.000000      0.391352
     0.00000      1.76500      1.76500         0.000000      0.000000     -0.397024
     0.00000      0.00000      3.53000         0.000000      0.000000      0.005117
     0.00000      1.76500      5.29500         0.000000      0.000000      0.391161
     0.00000      0.00000      7.06000         0.000000      0.000000     -0.390607
-----------------------------------------------------------------------------------
   total drift:                                0.000000      0.000000      0.016391

Last step:

POSITION                                       TOTAL-FORCE  (eV/Angst)
-----------------------------------------------------------------------------------
     0.00000      0.00000      0.00000         0.000000      0.000000      0.399012
     0.00000      1.76500      1.76500         0.000000      0.000000     -0.377003
     0.00000      0.00000      3.53000         0.000000      0.000000      0.105799
     0.00000      1.76500      5.32685         0.000000      0.000000     -0.062054
     0.00000      0.00000      7.02377         0.000000      0.000000     -0.065753
-----------------------------------------------------------------------------------
   total drift:                                0.000000      0.000000     -0.042925
  • Energy changes during relaxation from -25.556 to -25.571 eV which gives a relaxation energy of meV. Use p4vasp to check the convergence:

Fig Ni 100 surfrel 1.png

  • The surface energy of 0.86 eV for the unrelaxed surface is calculated in the following:

eV.

  • The surface energy of 0.84 eV for the relaxed surface is then calculated as:

eV.

  • The final geometry (from the CONTCAR or OUTCAR file) should look as follows:
fcc (100) surface
   3.53000000000000
     0.5000000000000000      0.5000000000000000      0.000000000000000
    -0.5000000000000000      0.5000000000000000      0.000000000000000
     0.0000000000000000      0.0000000000000000      5.000000000000000
   Ni
     5
Selective Dynamics
Direct
0.0000000000000000   0.0000000000000000   0.0000000000000000 F F F
0.0000000000000000   0.5000000000000000   0.1000000000000014 F F F
0.0000000000000000   0.0000000000000000   0.2000000000000028 F F F
0.5000000000000000   0.5000000000000000   0.3018043743226639 T T T
0.0000000000000000   0.0000000000000000   0.3979474020596729 T T T 
  • Inward relaxation of surface layers:
    • = ((0.3979-0.3018)-0.1)/0.1*100=-3.9%.
    • = ((0.3018-0.2000)-0.1)/0.1*100=+1.8%.
  • Use p4vasp to visualize the relaxation:

Fig Ni 100 surfrel 2.png

Download

Ni100clean_rel.tgz

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