Reweighting problem

[李云健]

when I do the metadynamics simulation, all the results is correct. However, when I want to reweight using the metad.rbias, I found the value is negative and the reweighting outcomes is not correct. I do not know the reason for this and how to resolve this problem. Here is the covar file and input files, thanks!

[guangpeng xue]

Hi, 

Has your problem solved? I also have the same confusion that why the bias potential can be negative sometimes. I think you were using Metadynamics, in my experiences of using MetaD, never got the negative value of bias potential, but currently using another method, I notice that the bias potential is no longer remain in positive ones. 

How do you think about that?

Many thanks!

Best wishes,

Guangpeng

[Michele Invernizzi]

Dear Guangpeng,

The bias potential can be shifted by any constant value without affecting the simulation (the forces remain the same) or the reweighting (it only adds a global shift to the FES). So, the fact that it is positive or negative is not a problem.

Regarding the original question, reweighting of metadynamics is a sensitive issue and several different methods have been proposed. A possible problem when using rbias for reweighting, is to correctly choose the length of the initial non-adiabatic equilibration part of the simulation to be discarded.

Best,

Michele 

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