[gmx-users] problem with exchange probabilities in remd

[OZGE ENGIN]

Hi all,

I am performing a remd simulation of a peptide+water system. I have tried different temperature distributions. I am using an NVT ensemble. My temperature coupling constant is 0.1 ps.

The problem is that upon increasing the temperature difference between the two replicas more than two (290==>294), the exchange probability decreases sharply, app. to 0.03. 

I have changed the exchange frequency in order to get a better exchange probabilities. However, it has not affected the overall exchange probabilities so much. 

Is there anybody who has encountered such a situation?

Thanks in advance
Ozge Engin
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Computational Science & Engineering
Koc University