[CP2K-user] [CP2K:16174] Keyword explanation: ON_THE_FLY_LOC

[Thomas Kühne]

Dear Nick, 

ON_THE_FLY_LOC is the implementation of the following paper: 
https://aip.scitation.org/doi/full/10.1063/1.2828507 <https://aip.scitation.org/doi/full/10.1063/1.2828507>
In the spirit of previous works of Thomas, Iftimie and Tuckerman, 
the orbital coefficient matrix of sought to be localized on-the-fly 
during the simulation. Contrary to the density matrix P, C is much 
more compact (MxN vs. MxM) but less sparse. This does not 
improve the stability/numerical stability, I would even argue quite 
the contrary. It’s one step towards efficient linear-scaling. In the 
limit of the corresponding localized orbitals MAY be equivalent to 
MLWF, but I conjecture in a numerical calculation there should be 
differences. 
To my understanding there is no specific reason for the combination 
with IRAC, except for that this had been implemented by the very 
same persons around the very same time: 
https://aip.scitation.org/doi/full/10.1063/1.2841077 <https://aip.scitation.org/doi/full/10.1063/1.2841077>

Cheers, 
Thomas

> Am 03.11.2021 um 00:21 schrieb Nicholas Winner <nwinner at berkeley.edu>:
> 
> Would anybody well versed in CP2K be able to provide a brief explanation of the ON_THE_FLY_LOC keyword, found inside the OT section. 
> 
> It says that it performs on the fly localization of the MOs, but nothing more. Does it help with convergence and/or numerical stability? It is also listed as only being compatible with the IRAC method, rather than the strict orthogonality algorithm.
> 
> Any explanation would be appreciated.
> 
> Best,
> -Nick
> 
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==============================
Thomas D. Kühne
Dynamics of Condensed Matter
Chair of Theoretical Chemistry
University of Paderborn
Warburger Str. 100
D-33098 Paderborn
Germany
thomas.kuehne at upb.de
+49/(0)5251/60-5726

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