[Wien] "Best" functional at the moment

[Peter Blaha]

The best general functional is r2scan. Energy, electron density and 
structure are in general the best you can have.

The scf implementation in WIEN2k is also NOT very costly and for bulk it 
converges quite well. Surfaces (large vacuum) could cause sometimes a 
problem. But of course: no forces.

Typically, the dielectric constant and Born charges are "related" to the 
band gap, and in scan this is not too much improved. Maybe mTASK is 
better for that property ?

For insulating (magnetic) transition metal compounds, mTASK might be 
better. It gives usually an insulator and not a metal (the scan-gaps and 
magnetic moments are only slightly improved). On the other hand, metals 
are probably not so well described by mTASK.

r2SCAN is quite bad for metallic Fe, Co, Ni, as it gives a much too 
large magnetic moment.

So the choice between mTASK or r2SCAN depends a bit on the type of 
compound and the properties of interest.


Am 01.05.2026 um 15:32 schrieb Laurence Marks:
> I have not been watching functional development of late, so a question: 
> What is "best" at the moment in terms of a combination of speed/ 
> accuracy. I do not want just band gaps, I want polarizability (e.g. Born 
> charges), work function, energy, electron dielectric constant and 
> energy. (I would love to also have forces, but I realise the issue.) I 
> don't know if mTASK, TASK or r2SCAN etc are best.
> 
> 
> -- 
> Emeritus Professor Laurence Marks (Laurie)
> Northwestern University
> Webpage <http://www.numis.northwestern.edu> and Google Scholar link 
> <http://scholar.google.com/citations?user=zmHhI9gAAAAJ&hl=en>
> "Research is to see what everybody else has seen, and to think what 
> nobody else has thought", Albert Szent-Györgyi
> 
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-- 
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Peter Blaha,  Inst. f. Materials Chemistry, TU Vienna, A-1060 Vienna
Email: peter.blaha at tuwien.ac.at
WWW:   http://www.imc.tuwien.ac.at      WIEN2k: http://www.wien2k.at
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