Unstable System

GROMACS version:2020.6
GROMACS modification: No
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Basically, my system was blowing up whenever I ran the production run. I tried almost everything for a month or so by reading the forums and questions related to the same.

After numerous attempts turning couple-intramol value to yes my production run ran fine .

I just want to know that turning this on is useful or not and why its default value is no .

I have a multi protein system on lipid membrane and has used parameterized CHARMM force field on GROMACS 2020.6.

I am new to the field and would be highly thankful if someone could spare there time to help me out here.

Thanks in advance.

are you performing a free energy calculation (that is mdp parameter opition free-energy=yes )?
The option couple-intramol means that the intra-molecular Van der Waals and Coulomb interactions are also turned on/off during a solvation or coupling free energy calculation.

Thanks for replying. I am performing free-energy calculations for a multi protein system on a membrane. But sadly, even after changing the default value, the production run failed later. Somehow, system minimization and equilibration runs smoothly without giving any error. I have tried almost everything related to it on internet. But nothing seems to work.