[CP2K-user] [CP2K:21806] Re: Cholesky decomposition failed

[Johann Pototschnig]

Cholesky decomposition computes a smaller representation of a tensor, which 
allows more efficient computations. 

It assumes a positive definite matrix, which, off course, numerically can 
not be guaranteed. 

It can be switched off, but certain functionalities will not work:
https://manual.cp2k.org/trunk/CP2K_INPUT/FORCE_EVAL/DFT/SCF.html#CP2K_INPUT.FORCE_EVAL.DFT.SCF.CHOLESKY
https://manual.cp2k.org/trunk/CP2K_INPUT/FORCE_EVAL/DFT/SCF/OT.html#CP2K_INPUT.FORCE_EVAL.DFT.SCF.OT.CHOLESKY

Most OT preconditioners use it. 



On Monday, September 8, 2025 at 11:22:16 AM UTC+2 Dat Ho wrote:

> Dear all,
>
>
> I am trying to perform ab initio MD simulations on a plain water box 
> containing 512 water molecules using the PW6B95 functional. The same input 
> works flawlessly for smaller boxes containing 64, 128 or 265 molecules, but 
> I can't seem to get it to work for 512 molecules. I always get the error 
> message 'Cholesky decomposition failed'. Can anyone spot an error in the 
> input? Also, what does this error message mean in detail? 
>
>
> Any help would be much appreciated!
>

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