Ni 111 surface relaxation

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Task

Relaxation of the first two layers of a Ni (111) surface.

Input

POSCAR

 fcc (111) surface
  3.53
   .70710678  .0000000  .000000
 -0.35355339 0.6123724  .000000
   .000000    .000000  5.1961524
    5
selective dynamics
direct
   .00000000   .00000000   .00000000  F  F  F
   .33333333   .66666667   .11111111  F  F  F
   .66666667   .33333333   .22222222  F  F  F
   .00000000   .00000000   .33333333  T  T  T
   .33333333   .66666667   .44444444  T  T  T

• Similar setup as for Ni 100 surface relaxation.
• Again 2 of 5 layers relaxed.
• [math]\displaystyle{ (1-.444)\cdot 5.196 \cdot 3.53 \approx 10.2 }[/math] [math]\displaystyle{ \AA }[/math] of vacuum.

INCAR

general:
  ISTART = 0
  ICHARG = 2
  SYSTEM = clean (111) surface
  ENMAX = 270
  ISMEAR = 2 ; SIGMA = 0.2
  ALGO = Fast
  EDIFF = 1E-6
    
dynamic:
  NSW = 100
  POTIM = 0.8
  IBRION = 1

• Same INCAR file as for Ni 100 surface relaxation, but spin polarization neglected.

KPOINTS

k-points
0
Monkhorst-Pack
9 9 1
0 0 0

Calculation

• N.B.: The setup for the calculation of the "bulk" energy can be found in the Ni111clean_rel/bulk subdirectory of the tar file.

• The sample output for the forces should look like the following:

POSITION                                       TOTAL-FORCE (eV/Angst)
-----------------------------------------------------------------------------------
     0.00000      0.00000      0.00000         0.000000      0.000000      0.178848
     0.00000      1.44112      2.03805         0.000000      0.000000     -0.060127
     1.24804      0.72056      4.07609         0.000000      0.000000      0.004418
     0.00000      0.00000      6.11522         0.000000      0.000000      0.036384
     0.00000      1.44112      8.14905         0.000000      0.000000     -0.159523
-----------------------------------------------------------------------------------
   total drift:                               -0.000084      0.000107     -0.017457

• Forces are already small at the beginning (small relaxations for compact surfaces).

• For surface energy non-spin-polarized bulk nickel as reference:
  • [math]\displaystyle{ \sigma^{\mathrm{unrel}} = \frac{1}{2} (-25.731 - 5 \cdot (-5.407)) = 0.65 }[/math] eV.
  • (111) surface more stable than (100) surface.*

• Two additional atom types (C and O) in the calculations: append C and O potentials to the POTCAR file.

Download

Ni111clean_rel.tgz

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