# Tag Info

## Hot answers tagged functional

Accepted

### What is the closest thing we have to "the" universal density functional?

I think this question somewhat comes down to what "camp" of DFT progression you subscribe to. I should specify upfront that this summary is mainly centered around molecular systems, so some of the ...
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### What are some recent developments in density functional theory?

2006 (Grimme): Double hybrid functionals The timeline of milestones you have given, includes a hybrid functional called B3LYP, which mixes a Hartree-Fock exchange functional with a GGA exchange-...
• 28.8k

### What are some recent developments in density functional theory?

2015 (Sun et al.): SCAN functional The SCAN meta-GGA functional is an extension of the popular PBE GGA [1] and the TPSS [2] and revTPSS [3] meta-GGAs, SCAN adheres to all 17 known exact XC ...

### What are some recent developments in density functional theory?

2013: Density-Corrected DFT (DC-DFT) The goal of Density-Corrected DFT (DC-DFT) is not only to get better accuracy but also to understand and correct the true error in the functional approximation.[1,...
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### What are some recent developments in density functional theory?

Dispersion corrected methods (2007/2010) Lots of answers already, I would say the main ones are covered. However, in the spirit of the question, I don't think anyone has done dispersion corrections ...

### What are some recent developments in density functional theory?

2004 (Yanai et al.): Range separation Often, the source of DFT improvement comes from Hartree-Fock as is also obvious from the answer involving double hybrid functionals. So too it is with range-...
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### What does B3LYP do well? What does it do badly?

B3LYP is still a decent functional at its level of theory (single-hybrid functional), but you're right that there's a general criticism of it, which I largely hear in the form of people saying things ...
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### What are some recent developments in density functional theory?

1993 (Becke): Hybrid Functionals Axel D. Becke introduced the adiabatic-connection model, which allows for mixing of DFT exchange and Fock-like exchange via the formula  E_{\text{x}} = a \cdot E^{\...
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### What are some recent developments in density functional theory?

1995 (Casida): TD-DFRT Time-Dependent Density Functional Response Theory is a linear response formulation of TDDFT for the calculation of excitation energies and corresponding transition amplitudes, ...
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Accepted

### What does B3LYP do well? What does it do badly?

I think this review¹ by Head-Gordon is a useful supplement to Nike's answer. Its combines a review of functional development, a benchmarking of various functionals, and an explanation of the design ...
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### What is the closest thing we have to "the" universal density functional?

I'm not entirely sure what you mean by "universal". If you mean a functional that can model a wide variety of materials with reasonable success, probably the closest we have are GGA functionals. ...
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Accepted

### Is LDA better than GGA for elastic constants?

I don't think you will find a reference showing that LDAs are better than GGAs for computing elastic constants. More specifically, I don't think a paper could reasonably offer an explanation of why ...
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### Mathematical expression of SCAN (Strongly Constrained and Appropriately Normed) constraints in DFT

Constraint #13: Size-Extensivity While the Wikipedia page for size-consistency and size-extensivity gives a clear formula for the definition of size-consistency, unfortunately they did not give a ...
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### What is the closest thing we have to "the" universal density functional?

This paper published by Bikash Kanungo, Paul M. Zimmerman & Vikram Gavini provide an interesting solution to getting closer to a "universal functional" Exact exchange-correlation potentials from ...
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### What does B3LYP do well? What does it do badly?

I don't have too much to add to the answers of Nike Dattani and Tyberius, but I think the crux is that its capabilities have been historically overestimated. One particular failing of B3LYP is that it ...
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### What are some recent developments in density functional theory?

2005 (Bartlett): ab initio DFT Basically one takes the xc functional from a wave function approach such as MBPT(2), CC, etc. and constructs an xc potential from them using density conditions or a ...
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### What are some recent developments in density functional theory?

I would add some developments in TDDFT that came around 1996 and resonated only later such as: the Casida equation (Casida 1995) that allows to calculate excitation energies and electronic spectra ...
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### What is the closest thing we have to "the" universal density functional?

Since this is a very active research topic the answer here might change regularly. Just within the last few months we've seen updates to the SCAN functional in the form of r2SCAN and the de-...
• 1,451
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### Total energy from KS-DFT: How reliable is it and why?

The main issue here is that the calculated energy is a potential energy, that's why the absolute value is useless. As potential energy always depends on a reference system, you can only use the ...
• 19k
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### DFT functionals from MP2 methods

These are called double hybrid functionals. You add a fraction of MP2 correlation on top of the DFT energy. A good reference is e.g. the review by Goerigk and Grimme from 2014 published in WIREs 4, ...
• 14.7k
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### Is the electronic band gap the only thing that is affected, when switching from standard KS-DFT to Hybrid functionals?

The band gap problem in DFT is not just due to approximate exchange-correlation functionals--it is a reflection of the fact that the Kohn-Sham (K-S) orbitals are a mathematical construction of a non-...
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### What are the best functionals for transition metal compounds?

The general question on the accuracy of density functionals for transition metal compounds is highly ambigious due to the effect of static correlation, for which there is no solution at the moment. ...
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### DFT functionals from MP2 methods

Susi is right that these are called double hybrids, I'll just add a bit more to complement that correct answer. My answer to "What are some recent developments in density functional theory?" ...
• 28.8k

### What are some recent developments in density functional theory?

Most chemists' point of view could be condensed as follows: Implementation of DFT in Gaussian (Pople et al, 1992) LDAs and GGAs were implemented in Gaussian 92/DFT by Pople, Gill and Johnson [Chem ...
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### Total energy from KS-DFT: How reliable is it and why?

Your question is on absolute energies, but all of your physical examples are relative energies. One could also add properties to the list; however, these are again not determined by the total energy, ...
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### What are the best functionals for transition metal compounds?

I think for transition metals the best functionals would be MS1-D3(0), ωB97M-V, ωB97X-V, MN15, and B97M-r based on the information from the review article-Thirty years of density functional theory in ...
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### What is the role of a chemist in computational chemistry?

In terms of the role of chemists for what you call the "most essential task": "What I understand is that the most essential task is the improvement of exchange correlation functionals ...
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### Are meta-GGA functionals SCAN (and its variants) ok to use in planewave DFT with the PBE pseudopotentials?

It is well known that using pseudopotentials generated with a functional which is inconsistent with the functional used in the plane-wave calculation can lead to serious problems, see here for example....
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### Is there a list of all functionals?

While it doesn't include intended uses directly and isn't necessarily exhaustive, check out the list of exchange-correlation functionals implemented by Libxc. There are a lot! They also include the ...
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