# Multiple tc-grps, does make any sense?

**URL:** <https://gromacs.bioexcel.eu/t/multiple-tc-grps-does-make-any-sense/6129>\
**Category:** User discussions\
**Created:** [April 6, 2023, 3:10pm UTC](https://gromacs.bioexcel.eu/t/multiple-tc-grps-does-make-any-sense/6129 "2023-04-06T15:10:40Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![fulvio](https://avatars.discourse-cdn.com/v4/letter/f/a88e57/32.png) [@fulvio](https://gromacs.bioexcel.eu/u/fulvio)\
**Post date:** [April 6, 2023, 3:10pm UTC](https://gromacs.bioexcel.eu/t/multiple-tc-grps-does-make-any-sense/6129/1 "2023-04-06T15:10:40Z")

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GROMACS version: 2023  
GROMACS modification: No

Dear gmx users,  
first of all, greetings, this is my first post here. I am shying entering the fascinating world of molecular simulations…  
I noticed that the nvt/npt/md.mdp files report in tc-grps that, by working on two groups will led to more accurate solutions. Now, I was wondering if working with multiple tc-groups is actually the best choice anyway, or if there are any drawbacks.  
Please, consider my case: I am working on a triple complex of a 50kDa enzyme bound to two different effectors in two different binding sites. I am following the usual way of action, by imposing two groups in tc-grps (Protein\_Ligand1\_Ligand2 Water\_and\_ions), but now I was wondering if here could be a better choice not to group the ligands with the protein, in this case putting “Protein Other Water\_and\_ions” thus considering three tc-grps. Of cource I generate the index file accordingly.  
Thank you in advance  
Fulvio

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**Author:** ![hess](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/hess/32/416_2.png) [@hess](https://gromacs.bioexcel.eu/u/hess)\
**Post date:** [April 6, 2023, 3:44pm UTC](https://gromacs.bioexcel.eu/t/multiple-tc-grps-does-make-any-sense/6129/2 "2023-04-06T15:44:49Z")

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Multiple temperature coupling groups is largely a relic from ancient MD times where algorithms were inaccurate and differential heating for different groups needed to be taken care of. Nowadays I see no good reason to use multiple temperature coupling groups, except for exotic cases such as non-equilibrium MD.

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**Author:** ![Pankaj](https://avatars.discourse-cdn.com/v4/letter/p/a9adbd/32.png) [@Pankaj](https://gromacs.bioexcel.eu/u/Pankaj)\
**Post date:** [August 2, 2024, 4:50am UTC](https://gromacs.bioexcel.eu/t/multiple-tc-grps-does-make-any-sense/6129/3 "2024-08-02T04:50:20Z")

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I am wondering if we use two tc-grps for solvent and solute in a binary system with same temperature and tau\_t and in another case if we use only one tc\_grps for the whole system then whether there would be any problem in the first case or both will be same?

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**Author:** ![hess](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/hess/32/416_2.png) [@hess](https://gromacs.bioexcel.eu/u/hess)\
**Post date:** [August 6, 2024, 1:41pm UTC](https://gromacs.bioexcel.eu/t/multiple-tc-grps-does-make-any-sense/6129/4 "2024-08-06T13:41:54Z")

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In practice there will not be any noticeable differences. But why use two groups when you can use one?