CASTEP > Tasks in CASTEP > Analyzing CASTEP results > Visualizing vibrational spectra

Visualizing vibrational spectra

When a CASTEP calculation returns a Hessian (dynamical matrix) at the Γ-point, then vibrational frequencies for the bonds in the system being studied can be calculated and visualized using the Vibrational Analysis tool.

After a CASTEP job that included calculation of the electric field response (i.e., the Polarizability, IR and Raman spectra checkbox was checked on the Properties tab of the CASTEP Calculation dialog) is complete and the results files have been downloaded successfully, Materials Studio will automatically import the Hessian matrix, provided that the CASTEP job was not a Properties run.

A dynamical matrix is returned if the TASK keyword in the input parameters (.param) file is set to either Efield or Phonon+Efield and there is a Γ-point among the phonon k-vectors. You can achieve this either by checking the Polarizability, IR and Raman spectra checkbox on the Properties tab of the CASTEP Calculation dialog or, alternatively, if you wish to calculate the phonon dispersion or phonon density of states, by checking the Phonons checkbox in the list on the Properties tab, checking the Dispersion or Density of states checkboxes, as appropriate, that appear below the list, and ensuring that there is a Γ-point in the q-vector set.

IR spectra

In order to carry out a vibrational analysis, you will need to import a Hessian matrix from the output of a CASTEP run.

To import a Hessian and display an IR spectrum

  1. Choose Modules | CASTEP | Analysis from the menu bar to display the CASTEP Analysis dialog.
  2. Select IR spectrum from the list of options at the top of the dialog.
  3. Ensure that the 3D Atomistic document to be updated is the active document.
  4. Click the Import Hessian from CASTEP output button.

If you requested that the electric field response be calculated as part of the CASTEP job by checking the Polarizability, IR and Raman spectra checkbox on the Properties tab of the CASTEP Calculation dialog, you will be able to display vibrational mode frequencies and absorption intensities for the structure being studied in the form of a list of values or graphically as a vibrational spectrum using the Vibrational Analysis tool.

Raman spectra

To display a Raman spectrum

  1. Choose Modules | CASTEP | Analysis from the menu bar to display the CASTEP Analysis dialog.
  2. Select Raman spectrum from the list of options at the top of the dialog.
  3. Use Results file selector to pick the right results file.
  4. Ensure that the 3D Atomistic document containing the structure is the active document.
  5. Select the Function of the mode to be calculated.
  6. If the Function is set to Intensity set the Temperature.
  7. Set the Smearing value to be used.
  8. Select the Units for the X axis.
  9. Specify whether to reverse the wavenumber and intensity axes.
  10. Click the View button.
  11. A new chart document, seedname Raman.xcd, is created in the results folder.
See Also:

Analyzing CASTEP results
Requesting vibrational properties
Requesting electric field response

Accelrys Materials Studio 8.0 Help: Wednesday, December 17, 2014
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