[CP2K-user] [CP2K:11276] Re: SCF convergence criterion options

[Thomas Kühne]

Hi, 

even though I agree with the comments made by Martin, I would like to add that only for TD 
EPS_SCF is the maximum norm of the difference between two subsequent density matrices. 
In case of OT, it is the mean deviation between the preconditioned gradients, which is a much 
weaker criterion! From this it follows first that in my opinion the change of energy is not the best 
choice of stopping criterion since it may be strongly dependent of the employed preconditioner 
and second that a calculations with TD and the default EPS_SCF value of 1.0E-6 is typically 
more accurate than the same calculation with EPS_SCF set to 1.0E-7. In other words, the 
choice of eigenvalue solver is much more important than the specific stopping criterion!

Best, 
Thomas

> Am 16.02.2019 um 12:18 schrieb M. Brehm <brehmin... at gmail.com>:
> 
> To the best of my knowledge, no other critera to signal SCF convergence are implemented in CP2k.
> 
> However, it is generally a bad idea to look at the SCF energy to determine if the SCF has converged... There exist quite common cases where the energy remains almost constant in some SCF iterations, but will heavily reduce later on. Many years of practical experience have shown that the norm of the difference between two subsequent density matrices is quite a good criterion.
> 
> Best regards,
> Martin
> 
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