# Error in missing hydrogen atoms

**URL:** <https://gromacs.bioexcel.eu/t/error-in-missing-hydrogen-atoms/3903>\
**Category:** User discussions\
**Tags:** forcefield, mdp-parameters, mdrun\
**Created:** [March 27, 2022, 3:48am UTC](https://gromacs.bioexcel.eu/t/error-in-missing-hydrogen-atoms/3903 "2022-03-27T03:48:31Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Santosh456](https://avatars.discourse-cdn.com/v4/letter/s/a8b319/32.png) [@Santosh456](https://gromacs.bioexcel.eu/u/Santosh456)\
**Post date:** [March 27, 2022, 3:48am UTC](https://gromacs.bioexcel.eu/t/error-in-missing-hydrogen-atoms/3903/1 "2022-03-27T03:48:31Z")

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GROMACS version:  
GROMACS modification: Yes/No  
Here post your question  
Is it good to ignore hydrogen using -ignh flag when names do not match?

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**Author:** ![alevilla](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/alevilla/32/439_2.png) [@alevilla](https://gromacs.bioexcel.eu/u/alevilla)\
**Post date:** [April 2, 2022, 10:40am UTC](https://gromacs.bioexcel.eu/t/error-in-missing-hydrogen-atoms/3903/2 "2022-04-02T10:40:31Z")

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Hi,  
If only hydrogen names do not match with the force field name, you can use gmx pdb2gmx with the option -ignh to let the tool add the H atoms. Then it is good to check if the H atoms, added by pdb2gmx, corresponds to the wanted one.  
/Alessandra

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**Author:** ![Santosh456](https://avatars.discourse-cdn.com/v4/letter/s/a8b319/32.png) [@Santosh456](https://gromacs.bioexcel.eu/u/Santosh456)\
**Post date:** [April 4, 2022, 4:40pm UTC](https://gromacs.bioexcel.eu/t/error-in-missing-hydrogen-atoms/3903/3 "2022-04-04T16:40:14Z")

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Thank You Maam