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# Ni 111 surface relaxation

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.
• ${\displaystyle (1-.444)\cdot 5.196\cdot 3.53\approx 10.2}$ ${\displaystyle \mathrm {\AA} }$ 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


### 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:
• ${\displaystyle \sigma ^{\mathrm {unrel} }={\frac {1}{2}}(-25.731-5\cdot (-5.407))=0.65}$ eV.
• (111) surface more stable than (100) surface.