# Hamiltonian REMD with Gromacs 2020.4 + Plumed 2.6.2

**URL:** <https://gromacs.bioexcel.eu/t/hamiltonian-remd-with-gromacs-2020-4-plumed-2-6-2/1241>\
**Category:** User discussions\
**Created:** [December 11, 2020, 10:41am UTC](https://gromacs.bioexcel.eu/t/hamiltonian-remd-with-gromacs-2020-4-plumed-2-6-2/1241 "2020-12-11T10:41:26Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Qinghua\_Liao](https://avatars.discourse-cdn.com/v4/letter/q/46a35a/32.png) [@Qinghua\_Liao](https://gromacs.bioexcel.eu/u/Qinghua_Liao)\
**Post date:** [December 11, 2020, 10:41am UTC](https://gromacs.bioexcel.eu/t/hamiltonian-remd-with-gromacs-2020-4-plumed-2-6-2/1241/1 "2020-12-11T10:41:26Z")

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GROMACS version: 2020.4  
GROMACS modification: Yes, interfaced with Plumed 2.6.2  
Here post your question

I was trying to run Hamiltonian REMD simulations with Gromacs 2020.4 and Plumed 2.6.2, but the simulations failed. I think the reason is that the flag -multi from mdrun was removed since Gromacs 2019.X, but only kept -multidir, while -multidir does not work properly with -hrex (for Hamiltonian REMD).

I used to run with Gromacs 2018.X, is there a way to solve this problem, or will the developers keep the flag -multi ? Thanks a lot!

All the best,  
Qinghua

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**Author:** ![NimaSoltani](https://avatars.discourse-cdn.com/v4/letter/n/d6d6ee/32.png) [@NimaSoltani](https://gromacs.bioexcel.eu/u/NimaSoltani)\
**Post date:** [December 15, 2020, 6:13pm UTC](https://gromacs.bioexcel.eu/t/hamiltonian-remd-with-gromacs-2020-4-plumed-2-6-2/1241/2 "2020-12-15T18:13:23Z")

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I recently tried to do the same kind of calculations with the same version as you mentioned. The modified package seems to have problems!  
In my case the simulation kept blowing up in the first few steps of simulation. However, the same topol.tpr file did not have any problem with the unmodified GROMACS code.

I suspect that multidir flag creates any problem, please look at the example here:

> **[Tutorial EDES / HADDOCK for ligand-protein docking](https://www.bonvinlab.org/education/biomolecular-simulations-2019/Metadynamics_tutorial/)**

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**Author:** ![Qinghua\_Liao](https://avatars.discourse-cdn.com/v4/letter/q/46a35a/32.png) [@Qinghua\_Liao](https://gromacs.bioexcel.eu/u/Qinghua_Liao)\
**Post date:** [December 29, 2020, 5:25pm UTC](https://gromacs.bioexcel.eu/t/hamiltonian-remd-with-gromacs-2020-4-plumed-2-6-2/1241/3 "2020-12-29T17:25:09Z")

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Thanks a lot for your reply!

Did you find a way to fix the issue?

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**Author:** ![NimaSoltani](https://avatars.discourse-cdn.com/v4/letter/n/d6d6ee/32.png) [@NimaSoltani](https://gromacs.bioexcel.eu/u/NimaSoltani)\
**Post date:** [January 14, 2021, 6:48pm UTC](https://gromacs.bioexcel.eu/t/hamiltonian-remd-with-gromacs-2020-4-plumed-2-6-2/1241/4 "2021-01-14T18:48:47Z")

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I would suggest using the [built-in HREX](https://manual.gromacs.org/documentation/2019/reference-manual/algorithms/replica-exchange.html) functionality of unmodified GROMACS