CO vibration: Difference between revisions

From VASP Wiki
No edit summary
 
(14 intermediate revisions by 3 users not shown)
Line 1: Line 1:
{{Template:At_and_mol}}
{{Template:At_and_mol - Tutorial}}


== Task ==
== Task ==
Calculation of the vibrational frequencies of a CO molecule.


== Input ==
== Input ==
Line 22: Line 24:
  {{TAGBL|SYSTEM}} = CO molecule in a box
  {{TAGBL|SYSTEM}} = CO molecule in a box
  {{TAGBL|ISMEAR}} = 0  ! Gaussian smearing
  {{TAGBL|ISMEAR}} = 0  ! Gaussian smearing
  {{TAGBL|IBRION}} = 5  ! use the conjugate gradient algorithm
  {{TAGBL|IBRION}} = 5  ! calculate second derivatives, Hessian matrix, and phonon frequencies
              ! from finite differences
  {{TAGBL|NFREE}} = 2    ! central differences
  {{TAGBL|NFREE}} = 2    ! central differences
  {{TAGBL|POTIM}} = 0.02 ! 0.02 A stepwidth  
  {{TAGBL|POTIM}} = 0.02 ! 0.02 A stepwidth  
  {{TAGBL|NSW}} = 1      ! ionic steps > 0
  {{TAGBL|NSW}} = 1      ! ionic steps > 0


=== {{TAG|KPOINTS}} ===
=== {{FILE|KPOINTS}} ===
  Gamma-point only
  Gamma-point only
   0
   0
Line 35: Line 38:


== Calculation ==
== Calculation ==
*The selected degrees of freedom are displaced once in the direction <math>\hat{x}</math> and once in <math>-\hat{x}</math> by 0.02 <math>\AA</math> ({{TAG|POTIM}}).
*In the present case this makes 4 displacements plus the equilibrium positions (i.e. a total of five ionic configurations).
=== {{TAG|OUTCAR}} ===
At the end of the {{TAG|OUTCAR}} file the following output should be obtained:
SECOND DERIVATIVES (NOT SYMMETRIZED)
------------------------------------
              1Z          2Z
  1Z  -114.737304  114.737304
  2Z  114.458316 -114.458316
 
 
Eigenvectors and eigenvalues of the dynamical matrix
----------------------------------------------------
   
 
  1 f  =  63.887522 THz  401.417139 2PiTHz 2131.058277 cm-1  264.217647 meV
            X        Y        Z          dx          dy          dz
      0.000000  0.000000  0.000000            0          0  -0.655280
      0.000000  0.000000  1.143000            0          0    0.755386
  2 f/i=    0.038494 THz    0.241864 2PiTHz    1.284016 cm-1    0.159198 meV
            X        Y        Z          dx          dy          dz
      0.000000  0.000000  0.000000            0          0  -0.755386
      0.000000  0.000000  1.143000            0          0  -0.655280


== Download ==
== Download ==
[http://www.vasp.at/vasp-workshop/examples/COvib.tgz COvib.tgz]
[[Media:COvib.tgz| COvib.tgz]]
----
[[VASP_example_calculations|To the list of examples]] or to the [[The_VASP_Manual|main page]]
{{Template:At_and_mol}}
 
Back to the [[The_VASP_Manual|main page]].


[[Category:Examples]]
[[Category:Examples]]

Latest revision as of 11:00, 13 November 2019

Task

Calculation of the vibrational frequencies of a CO molecule.

Input

POSCAR

CO molecule in a box
 1.0          ! universal scaling parameters
 8.0 0.0 0.0  ! lattice vector  a(1)
 0.0 8.0 0.0  ! lattice vector  a(2)
 0.0 0.0 8.0  ! lattice vector  a(3)
1 1           ! number of atoms for each species
sel           ! selective degrees of freedom are changed
cart          ! positions in cartesian coordinates
 0 0 0       F F T  ! first atom
 0 0 1.143   F F T  ! second atom

Alternatively, try to fix one of the atoms completely.

INCAR

SYSTEM = CO molecule in a box
ISMEAR = 0   ! Gaussian smearing
IBRION = 5   ! calculate second derivatives, Hessian matrix, and phonon frequencies
             ! from finite differences
NFREE = 2    ! central differences
POTIM = 0.02 ! 0.02 A stepwidth 
NSW = 1      ! ionic steps > 0

KPOINTS

Gamma-point only
 0
Monkhorst Pack
 1 1 1
 0 0 0

Calculation

  • The selected degrees of freedom are displaced once in the direction and once in by 0.02 (POTIM).
  • In the present case this makes 4 displacements plus the equilibrium positions (i.e. a total of five ionic configurations).

OUTCAR

At the end of the OUTCAR file the following output should be obtained:

SECOND DERIVATIVES (NOT SYMMETRIZED)
------------------------------------
              1Z          2Z
 1Z  -114.737304  114.737304
 2Z   114.458316 -114.458316
  
  
Eigenvectors and eigenvalues of the dynamical matrix
----------------------------------------------------
   
  
  1 f  =   63.887522 THz   401.417139 2PiTHz 2131.058277 cm-1   264.217647 meV
            X         Y         Z           dx          dy          dz
     0.000000  0.000000  0.000000            0           0   -0.655280
     0.000000  0.000000  1.143000            0           0    0.755386
  2 f/i=    0.038494 THz     0.241864 2PiTHz    1.284016 cm-1     0.159198 meV
            X         Y         Z           dx          dy          dz
     0.000000  0.000000  0.000000            0           0   -0.755386
     0.000000  0.000000  1.143000            0           0   -0.655280

Download

COvib.tgz

Back to the main page.