[CP2K-user] [CP2K:22223] Re: Extrapolation formula for basis set convergence

[Riccardo Pezzetta]

Sorry I wrote the wrong link for the article, the DOI is 10.1021/ct4002202

Riccardo Pezzetta

Il giorno mercoledì 6 maggio 2026 alle 12:37:59 UTC+2 Riccardo Pezzetta ha 
scritto:

> Dear all,
> I am doing a calculation for the binding energy of the argon dimer with 
> RPA and I used as primary basis sets aug-cc-pVTZ and aug-cc-pVQZ. In the 
> CP2K maual I saw that I have to use the extrapolation formula E(X)=A+B/X^3 
> for correlation energies, but I don't know how to extrapolate the EXX 
> energy. In the article https://pubs.acs.org/journal/jctcce I saw that 
> they use the extrapolation formula for the cohesive energies instead of 
> correlation energies. So I tried to make the extrapolatoin in two ways:
> 1) I calculated the binding energy of the dimer with TZ and QZ basis sets 
> separately and made the cubic extrapolation with the resulting bonding 
> energies
> 2) I made the extrapolation with the cubic formula with absolute RPA and 
> EXX energies for the dimer and the atom separately and after that I 
> calculated the bonding energy with the extrapolated results.
> With the first method I get E bonding = -8.4 meV, with the second one I 
> get E bonding = -8.6 meV.
> Are these procedures correct? Since the results are similar can I deduce 
> that both methods are correct? In both cases the atom calculation has been 
> made with a ghost atom with the same geometry of the dimer in order to take 
> into account the basis set superposition error.
> Kind regards;
>
> Riccardo Pezzetta

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