Questions tagged [electron-correlation]

Questions relating to electron correlation - the interaction between electrons in the electronic structure of a quantum system. The correlation energy is a measure of how much the movement of one electron is influenced by the presence of all other electrons.

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31
votes
1answer
371 views

What correlation effects are included in DFT?

In wavefunction methods the accuracy of the description of a system of electrons can be improved systematically starting from a reference, usually a Hartree-Fock wavefunction. This difference between ...
10
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1answer
79 views

How does static correlation differ from Fermi correlation, and how does dynamic correlation differ from Coulomb correlation?

From what I read, the correlation energy can be grouped as static correlation and dynamic correlation. Another way to group them is Fermi correlation and Coulomb correlation. Is there any link between ...
23
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5answers
615 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 ...
25
votes
2answers
220 views

How to determine, a priori, whether a compound has multireference character?

We say a system has multireference character if it is not well described at the SCF level by a single configuration/Slater determinant. Not accounting for this can lead to errors in post-SCF methods, ...
11
votes
0answers
82 views

What are the ways to add dynamic correlation to an MCSCF wavefunction?

We recently learned about the many types of MCSCF, which treat "static" electron correlation. There are then many ways to treat further "dynamic" electron correlation to try and ...
12
votes
1answer
112 views

What are the practical limitations of R12/F12 methods?

Electron correlation methods based on an expansion of the $N$-electron wavefunction in terms of Slater determinants have a slow basis set convergence. Moreover, explicitly correlated methods (such as ...
17
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1answer
250 views

What is static correlation, actually?

My question is inspired by this question and also this one. I have come across the term static correlation multiple times. Introduction to Computational Chemistry by Frank Jensen describes static (or ...
12
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3answers
130 views

Physically motivated double hybrid DFT?

This question came to mind while writing another question here Extended Hybrid Methods, but I felt it was distinct enough to ask separately. In double hybrids DFT methods, you essentially perform a ...
11
votes
1answer
104 views

Is there any relation between static correlation and finite-temperature smearing?

I am new to this field, so there is a chance that I am mixing two entirely different concepts together, but it seems to be that static correlation and finite-temperature smearing in DFT are somehow ...
10
votes
2answers
83 views

Quantifying electronic overlap?

I am trying to understand how to quantify the electronic interaction/conduction/overlap between two metal cores at varying distances. As someone who works primarily with classical MD, and has less ...