Vibrational frequencies of CO on Ni 111 surface

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Task

Calculation of the vibrational frequencies of CO@Ni(111) (on top).

Input

POSCAR

Ni - (111) + CO on-top                  
   3.53000000000000     
     0.7071067800000000    0.0000000000000000    0.0000000000000000
    -0.3535533900000000    0.6123724000000000    0.0000000000000000
     0.0000000000000000    0.0000000000000000    5.1961523999999999
   Ni   C    O 
     5     1     1
Selective dynamics
Direct
  0.0000000000000000  0.0000000000000000  0.0000000000000000   F   F   F
  0.3333333300000021  0.6666666699999979  0.1111111100000031   F   F   F
  0.6666666699999979  0.3333333300000021  0.2222222199999990   F   F   F
 -0.0000000000000000  0.0000000000000000  0.3326227833039623   F   F   F
  0.3333333300000021  0.6666666699999979  0.4445699380869117   F   F   F
  0.3333333300000021  0.6666666699999979  0.5403264650180125   F   F   T
  0.3333333300000021  0.6666666699999979  0.6032949698060487   F   F   T
 
  0.00000000E+00  0.00000000E+00  0.00000000E+00
  0.00000000E+00  0.00000000E+00  0.00000000E+00
  0.00000000E+00  0.00000000E+00  0.00000000E+00
  0.00000000E+00  0.00000000E+00  0.00000000E+00
  0.00000000E+00  0.00000000E+00  0.00000000E+00
  0.00000000E+00  0.00000000E+00  0.00000000E+00
  0.00000000E+00  0.00000000E+00  0.00000000E+00

• Frequencie only for CO molecule and z-direction (z- and (x,y) are independent).

INCAR

 SYSTEM = CO on Ni111 - frequencies
    
general:
  ENMAX  = 400
  ISMEAR =    2  ; SIGMA = 0.2
  ALGO   = Fast
  EDIFF  = 1E-6
  MAXMIX = 60  # reuse the mixer between ionic steps, saves time
    
dynamic:
  NSW = 100
  IBRION = 5
  NFREE  = 2

• Small termination criterion (EDIFF).
• Automatic frequency calculation (displacement 0.04 $\mathrm {\AA}$).
• Reuse of the mixer between ionic steps (MAXMIX) to save time.

KPOINTS

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

Calculation

• Finite differences give the following additional output in the OUTCAR fiel for frequency calculations:

Finite differences progress:
 Degree of freedom:   1/  2
 Displacement:        1/  2
 Total:               1/  4

• After the first calculation for the equilibrium geometry, NFREE displacements ($\pm$POTIM) are performed for each degree of freedom. From these displacements the dynamical matrix is set up and diagonalized.

• At the end of the OUTCAR file the following are listed:
  • Forces.
  • The dynamical matrix and finally.
  • The eigenfrequencies.
  • Eigenvectors (first normalized and then mass-weighted).

• Try to change the selective dynamics tag such that displacements

in x and y direction are allowed as well for CO (note that the selective dynamics flags always refer to cartesian coordinates), i.e,

 0.3333333300000021  0.6666666699999979  0.5403264650180125   F   F   T
 0.3333333300000021  0.6666666699999979  0.6032949698060487   F   F   T

to

 0.3333333300000021  0.6666666699999979  0.5403264650180125   T   T   T
 0.3333333300000021  0.6666666699999979  0.6032949698060487   T   T   T

Also test whether you need to decrease EDIFF to 1E-8.

Download

COonNi111_freq.tgz

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