[CP2K:3177] Re: error in bond dissociation energy of gas phase molecule

Teodoro Laino teodor... at gmail.com
Thu Apr 7 06:26:22 CEST 2011


Hi Jun,

I was wondering: did you try with a different XC functional ?
Could you do the same test with PBE  and GPW (comparing cp2k and gaussian) ?

Thanks
Teo

On Apr 6, 2011, at 11:09 PM, Jun wrote:

> Many thanks for the comments, Fawzi.
> 
>> That is exactly what I wanted to comment on:
>> 1) GTH is a pseudopetential, and also has scalar relativistic  
>> correction (should be small in this case, but you never know)
> 
> I guess relativistic correction in O pseudopotential might be too
> small to lower the binding energy by 0.5 eV. Possibly, something else
> in the pseudopotential.
> 
>> 2) basiset for GTH pseudopotential are different from those on all  
>> electrons, they should be more or less comparable, but there is no  
>> guarantee, what can be compared is the basset limit in both cases
> 
> We used the same basis set as used in Gaussian (6-31g*).  The basis
> set convergence was checked in Gaussian, and the calculated binding
> energy is the same as in literature.
> 
>> 3) a cutoff of 280 for OH is a bit on the low side, especially if you  
>> don't do any smoothing of the xc part, I would increase that
> 
> We did check this. Increasing the cutoff to 400 doesn't make a
> difference.
> In the all electron calculation, the cutoff seems even lower than 280
> (directly taken from sample input without any change). We should check
> this. But not sure this could be the cause of the increase of 0.8 eV
> in binding energy. I am more concerned on the other settings for GAPW
> calculations I don't understand.
> 
> Cheers,
> Jun
> 
> 
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