[CP2K-user] [CP2K:19078] Re: MIN_DISP keyword for Metadynamics

[Marcella Iannuzzi]

Dear Alex, 

This key seems to be there to anticipate the collocation of a new hill, if 
the displacement in the CV space is larger than the given threshold. 
The modulo of the CV-displacement vector is calculated and compared to 
min_disp. 
No distinction among different CVs are considered. I agree that it is not 
obvious how to sum up together distances, angles or coordination numbers, 
and which threshold would make sense for an heterogeneous selection of CVs. 
I would tune it on the CV with the largest fluctuation, which is going to 
be dominant in the 
calculation of the displacement vector.   
The idea is to be in another place of the CV-space, with respect to the 
previous collocation (only the previous, no history is taken into account), 
just not to place two subsequent hills one on top of the other. Hence if 
the sampling moves enough in one direction, the condition is fulfilled. 
For Lagrangian MTD the auxiliary variable are used.

Regards,
Marcella

On Friday, July 7, 2023 at 4:51:56 AM UTC+2 Alex Brown wrote:

> Dear CP2K Experts,
>
> I was reading about using minimum displacement (MIN_DISP 
> <https://manual.cp2k.org/trunk/CP2K_INPUT/MOTION/FREE_ENERGY/METADYN.html#MIN_DISP> 
> keyword) during Metadynamics where new hills are placed only after a 
> minimum displacement in hills. 
>
> My question is which CV dimension is considered in this displacement? If I 
> use two CV's will the code look for the MIN_DISP in both CV before placing 
> a new hill or just one? I am just confused how this will work if the two 
> CV's have different fluctuations where one CV fluctuates more than the 
> other. Also with Lagrangian version of Metadynamics, will the code look for 
> displacement in auxiliary variable or real variable?
>
> Thanks,
> Alex
>

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