Why I get a 5000 cm-1 vibration frequency for single H2 molecule?

[Jingyun Ye]

Hi, Flo

Thanks very much. I checked the data in cccbdb. It really depends on the 
basis set. I have a another question and hope you have some idea. Why did 
only get 3 vibration modes for CO2 ? The degenerate modes around 600 cm-1 
should have two but only shows one in my output. And I still checked the 
cccbdb data base. There are 3 frequency modes for CO2 molecule shown in the 
table. And in the full list, there indeed has 4 modes. I also got 3 modes 
for CO2 before when I used VASP.  

Another question:  In the .mol  file of single CO2 frequency calculation, I 
only got 3 modes which no rotation or translation modes. But when I put the 
CO2 in porous material to study the adsorption property, the .mol file has 
the rotation and translation modes for CO2. I just want to know how does 
this happen? I remember Alex mentioned in previous posts that the CP2K 
output will automatically purify the R and T modes. If this is true, how 
does the R and T modes shows in the outputs for CO2 in porous material but 
don't show for single CO2 molecule.  (Note: all the input files are same 
with my post one.)

Thanks very much for your help!



Thanks again!


On Thursday, December 4, 2014 5:31:37 AM UTC-5, Florian Schiffmann wrote:
>
> Hi,
>
> looking at cccbdb, you can see that using a bad basis can have a miserable 
> effect. In your case a DZVP-SR basis has the same effect, remove if you use 
> the normal DZVP optimize and run the analysis you will get a pretty nice 
> frequency
>
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