frequency

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acharyachethan · #1 Post by **acharyachethan** » Wed Apr 26, 2006 4:38 am

Hi:

Can I perform frequency calculations (IBRION=5) at a specific temperature, say 400C? If I can, could you tell me how?

Thanks,

Chethan

tjf · #2 Post by **tjf** » Wed Apr 26, 2006 9:02 am

*Error* *Does not compute*

(Sorry, couldn't resist.)

Short answer: No.

Harmonic frequencies are independent of temperature. Maybe you should rethink what information you are tying to get about your system. (Maybe also revisit a physical chemistry textbook or two?)

acharyachethan · #3 Post by **acharyachethan** » Wed Apr 26, 2006 8:05 pm

I'm sorry to put the question incorrectly. What I meant was, can I get thermochemical data, like vibrational, rotational, etc. energies of adsorbed species on surfaces as a function of temperature with IBRION=5 based on harmonic vibrational frequencies with an additional temperature tag?

bandy · #4 Post by **bandy** » Thu Apr 27, 2006 8:11 am

ZPE and Thermal corrections could be calculated for the (adsorbate+substrate) system once you know harmonic frequencies of all the modes (I mean 3N-6). But VASP provides information for the selective modes. However, you can calculate partial ZPE and Th. corr. for a part of the system for e.g. adsorbate plus a few adsorbent atoms where adsorbate species is attached. I have a code which does that or you can write a simple code to do that.

bandy

hlzya · #5 Post by **hlzya** » Sat Apr 29, 2006 1:30 am

what can your code do?

[quote="bandy"]ZPE and Thermal corrections could be calculated for the (adsorbate+substrate) system once you know harmonic frequencies of all the modes (I mean 3N-6). But VASP provides information for the selective modes. However, you can calculate partial ZPE and Th. corr. for a part of the system for e.g. adsorbate plus a few adsorbent atoms where adsorbate species is attached. I have a code which does that or you can write a simple code to do that.

bandy[/quote]