# Tag Info

23

First note that the acronym DFA I used in my comment originates from Axel D. Becke paper on 50 year anniversary of DFT in chemistry: Let us introduce the acronym DFA at this point for “density-functional approximation.” If you attend DFT meetings, you will know that Mel Levy often needs to remind us that DFT is exact. The failures we report at ...

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There is nothing trivial about MCSCF calculations because it is hard to predict a priori how long a calculation will take. There are well-defined equations for calculating how many determinants $$D(n,N,S) = \binom{n}{N/2+S} \binom{n}{N/2-S}$$ or configuration state functions (CSFs) $$D(n,N,S) = \frac{2S+1}{n+1} \binom{n+1}{N/2-S} \binom{n+1}{N/2+S+1}$$...

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It is generally recommended not to use a cc basis set with a DFT method (and I guess conversely, a basis set aimed at DFT should not be used with a coupled cluster method). This statement glosses over some specifics that might be important. There is nothing technically wrong with using correlation-consistent or ANO basis sets with DFT, unless the basis is ...

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2

Originally, I was convinced that the molecular geometry has very limited influence on the virial ratio: only in so far as the effective basis set will change with the geometry as long as nuclei-centered Slater or Gauss (STO or GTO) basis functions are used.1 Hartree-Fock is accurate as full CI (within the given basis set and its postulates and earlier ...

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