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### Can the VTST toolkit generate the Raman spectrum of a system?

Posted: **Mon Sep 02, 2019 12:46 am**

by **jianmin**

Dear all and especially Prof. Graeme,

My question is as the title of my post indicates: can the VTST toolkit generate the Raman spectrum of a system? If it can, is there is guide for doing that?

Thanks.

### Re: Can the VTST toolkit generate the Raman spectrum of a system?

Posted: **Mon Sep 02, 2019 3:41 am**

by **naman_katyal**

Hi

To calculate the Raman response you need the derivative of polarizability with respect to the normal mode for all the normal modes for a given system. For this you first need to find the normal modes which can be done using VTST and generate these two files : freq,dat and modes_sqrt_amu.dat. (you can use dymmatrix.py script to get these two files after normal mode calculations). These two files can then be used to setup VASP calculations to find the Raman response using LEPSILON = True tag.

What I would suggest is follow this link:

https://github.com/raman-sc/VASP
This is free python script which will help you Raman response for the normal modes of a given system using VTST in background.

Note: If you use VASP IBRION=5 to find the normal mode then you must have NWRITE = 3 tag in your INCAR to write the Eigenvectors and eigenvalues of the dynamical matrix in OUTCAR.