AMBER Archive (2005)

Subject: Re: AMBER: No exchange among replicas in REMD!

From: Carlos Simmerling (carlos_at_ilion.bio.sunysb.edu)
Date: Sun Dec 18 2005 - 16:26:42 CST

if you haven't already, you should read some of the
articles that describe the replica exchange method.
the exchange frequency is determined by the replica
temperatures and the system size. you may have the replicas
too far apart. the program uses the potential energies
of the two replicas and the temperature to determine
the exchange. it is not random.

Peng Tao wrote:

> Dear all,
>
> Thanks for the previous help on REMD in AMBER8.
>
> Now I am trying to run REMD on of my systems. But in one REMD run
> with 12 replicas, I didn's see any exchange between any replicas
> pair when I set numexchg as 200. I did set rem as 1, when I submitted
> REMD job.
>
> I don't know if this is normal for REMD or not. I also want know how
> to control how frequent the real exchanges happen during the REMD run.
> It seems to me that REMD randomly chooses if there is exchange or not,
> and how many pairs of replicas exchange temperatures. But it is not
> clear how to control

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