# Which is prefererable for production run “constraints = all-bonds” or “constraints = h-bonds” nd why

**URL:** <https://gromacs.bioexcel.eu/t/which-is-prefererable-for-production-run-constraints-all-bonds-or-constraints-h-bonds-nd-why/3583>\
**Category:** User discussions\
**Created:** [February 2, 2022, 10:25am UTC](https://gromacs.bioexcel.eu/t/which-is-prefererable-for-production-run-constraints-all-bonds-or-constraints-h-bonds-nd-why/3583 "2022-02-02T10:25:25Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![dsaha](https://avatars.discourse-cdn.com/v4/letter/d/59ef9b/32.png) [@dsaha](https://gromacs.bioexcel.eu/u/dsaha)\
**Post date:** [February 2, 2022, 10:25am UTC](https://gromacs.bioexcel.eu/t/which-is-prefererable-for-production-run-constraints-all-bonds-or-constraints-h-bonds-nd-why/3583/1 "2022-02-02T10:25:25Z")

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GROMACS version: 2020.6  
GROMACS modification: No  
Here post your question

Actually I am confused in taking what constraint parameter i.e“constraints = all-bonds” or “constraints = h-bonds” will be suitable for nvt and npt production run. Is there any documentation or link from where I can understand the details.

Thanks in advance

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**Author:** ![awacha](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/awacha/32/19_2.png) [@awacha](https://gromacs.bioexcel.eu/u/awacha)\
**Post date:** [February 2, 2022, 10:46am UTC](https://gromacs.bioexcel.eu/t/which-is-prefererable-for-production-run-constraints-all-bonds-or-constraints-h-bonds-nd-why/3583/2 "2022-02-02T10:46:50Z")

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Dear dsaha,

this typically depends on how the force field you are using was parametrized: I’d keep it that way as the FF recommends. The MDP option you are looking for is documented here (with the others):

In short, if you use ‘h-bonds’, bonds between hydrogens and heavy atoms will be treated as rigid rods, instead of harmonic oscillators. ‘all-bonds’ makes all bonds (i.e. between heavy atoms, too) behave as rigid rods.

Hope that helps,

Andras

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**Author:** ![dsaha](https://avatars.discourse-cdn.com/v4/letter/d/59ef9b/32.png) [@dsaha](https://gromacs.bioexcel.eu/u/dsaha)\
**Post date:** [February 2, 2022, 2:40pm UTC](https://gromacs.bioexcel.eu/t/which-is-prefererable-for-production-run-constraints-all-bonds-or-constraints-h-bonds-nd-why/3583/3 "2022-02-02T14:40:41Z")

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Dear Andras,  
Thanks for the response. It helped me to understand.

Regards  
Debanjan