[gmx-users] Hamiltonian replica exchange umbrella sampling with gmx 4.6

[Joakim Jämbeck]

Dear gmx-users,

I am currently trying to runt Hamiltonian replica exchange umbrella sampling in hope to do some better sampling.

I have generated a number of tpr-files along my reaction coordinate and they all run fine in independent simulations. The issue comes when I would like the replica exchange to start.

The following line is used to initiate the exchange:

mdrun_mpi -replex 1000 -s md -pf pullf -px pullx -multi 40 -maxh 0.5

All replicas have the same temperature and the following error is what I face seconds after submitting the job:

The properties of the 40 systems are all the same, there is nothing to exchange
For more information and tips for troubleshooting, please check the GROMACS
website at http://www.gromacs.org/Documentation/Errors

I could simply change the temperature between the replicas by 0.001 K and it would run I think. But that is not very elegant.

Does anyone have any suggestions?

Thanks in advance!

Best regards,
Joakim