All Questions
Tagged with electron-correlation quantum-chemistry
5 questions
7
votes
2
answers
199
views
Why is electron correlation called the "chemical glue"?
A significant part of quantum chemistry involves developing methods that go beyond the Hartree-Fock theory which treats electron-electron interactions through a mean-field approach. From what I ...
- 271
15
votes
1
answer
711
views
Why are Norm-conserving Pseudopotentials considered so important?
So I am aware that a norm-conserving pseudopotential enforces the conditions that:
Inside the cut-off radius, the norm of each pseudo-wavefunction is identical to its corresponding all-electron ...
- 861
14
votes
1
answer
1k
views
When do we abandon ab initio methods?
This question is related to (and was originally asked in) another post about "quantum protectorates" I made here.
Ab initio methods are nice because they directly solve a sort of "...
- 741
5
votes
1
answer
260
views
What are the other matrix elements in singlet symmetry-adapted CISD?
Szabo/Ostlund list the CI matrix elements between singlet symmetry-adapted configurations (SAC) in Table 4.1 of their book:
$$
\langle ^1\Psi^r_ a \lvert \mathcal{H} - E_ 0 \rvert ^1\Psi^r_ a \rangle,
...
- 1,708
30
votes
5
answers
3k
views
When and Why does Density Functional Theory (DFT) fail?
Every method has its strengths and weaknesses. For instance, a strength of DFT is that is has HF like speeds, but can also account for electron-correlation and this is a pretty big feature since ...
- 4,416