Hamiltonian Replica Exchange has been implemented in Gromacs. However, a proper procedure to perform H-REMD is not available. Any help on this topic is highly appreciable. Thanks.
The easiest way of running H-REMD in Gromacs is to use a recent Plumed patch. Check the links for details:
http://dx.doi.org/10.1080/00268976.2013.824126
http://plumed-code.org
In Munich, they have their own in-house modification of Gromacs: http://dx.doi.org/10.1021/ci500296f You may also wish to ask them, though Plumed seems to work just fine.