Faster way to calculate isotopic vibration frequencies?

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tanggara · #1 Post by **tanggara** » Thu Jan 05, 2012 7:53 pm

Hi, is there any other way to calculate isotopic vibration frequencies other than changing the POMASS in the POTCAR? I'm using IBRION=5, POTIM=0.01, NSW=1, NFREE=2, and ISIF=2 in the INCAR.

alex · #2 Post by **alex** » Fri Jan 06, 2012 11:45 am

Hi!

Are you talking about changing e.g. H to D and observing the change in the wavenumbers of some modes?

Cheers,

alex

tanggara · #3 Post by **tanggara** » Mon Jan 09, 2012 11:01 pm

Hi Alex,

Thank you for responding. That is right, I'd like to see the shift of the wavenumber e.g. H to D of some modes.

alex · #4 Post by **alex** » Tue Jan 10, 2012 10:02 am

Hi,

the fast answer is 'yes', it's possible: you have to use the Hessian out of OUTCAR and manipulate it accordingly (-> textbook).

Cheers,

alex

tanggara · #5 Post by **tanggara** » Tue Jan 10, 2012 5:38 pm

Hi Alex,

Thank you for the answer! I am aware that grabbing the Hessian and manipulating it will result in being able to calculate the change in wavenumber on isotopic shift. Yet, I was curious to know whether there is a flag where VASP (or a script that) can do this manipulation accordingly. If not, the manual calculation is the way to go then. Thank you again Alex for the helpful information!