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
- Frequencies only for the CO molecule and the z-direction (z- and (x,y) are independent).
N.B.: this POSCAR is essentially the result (CONTCAR file) of the relaxation performed in the CO on Ni 111 surface example.
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 ).
- 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 (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).
- The example output for the eigenvectors and eigenvalues of the dynamical matrix from the OUTCAR file should look like the following:
Eigenvectors and eigenvalues of the dynamical matrix
----------------------------------------------------
1 f = 63.914144 THz 401.584411 2PiTHz 2131.946301 cm-1 264.327748 meV
X Y Z dx dy dz
0.000000 0.000000 0.000000 0 0 0
0.000000 1.441116 2.038046 0 0 0
1.248043 0.720558 4.076093 0 0 0
0.000000 0.000000 6.108743 0 0 0
0.000000 1.441116 8.153979 0 0 0
0.000000 1.441116 9.908620 0 0 -0.761748
0.000000 1.441116 11.063296 0 0 0.623594
2 f = 12.467410 THz 78.335050 2PiTHz 415.868035 cm-1 51.561083 meV
X Y Z dx dy dz
0.000000 0.000000 0.000000 0 0 0
0.000000 1.441116 2.038046 0 0 0
1.248043 0.720558 4.076093 0 0 0
0.000000 0.000000 6.108743 0 0 0
0.000000 1.441116 8.153979 0 0 0
0.000000 1.441116 9.908620 0 0 -0.623594
0.000000 1.441116 11.063296 0 0 -0.781748
As one can see the first vibrational mode is the so-called CO stretch mode (stretching and contracting the C-O bond), whereas the second mode shows the CO molecule moving w.r.t. to the metallic surface (CO-metal).
- 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
Overview > Ni 100 surface relaxation > Ni 100 surface DOS > Ni 100 surface bandstructure > Ni 111 surface relaxation > CO on Ni 111 surface > Ni 111 surface high precision > partial DOS of CO on Ni 111 surface > vibrational frequencies of CO on Ni 111 surface > STM of graphite > STM of graphene > collective jumps of a Pt adatom on fcc-Pt (001): Nudged Elastic Band Calculation > List of tutorials