# Group Water\_and\_ions referenced in the .mdp file was not found in the index file

**URL:** <https://gromacs.bioexcel.eu/t/group-water-and-ions-referenced-in-the-mdp-file-was-not-found-in-the-index-file/4383>\
**Category:** User discussions\
**Created:** [June 29, 2022, 9:58am UTC](https://gromacs.bioexcel.eu/t/group-water-and-ions-referenced-in-the-mdp-file-was-not-found-in-the-index-file/4383 "2022-06-29T09:58:06Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![antkumar73](https://avatars.discourse-cdn.com/v4/letter/a/eb9ed0/32.png) [@antkumar73](https://gromacs.bioexcel.eu/u/antkumar73)\
**Post date:** [June 29, 2022, 9:58am UTC](https://gromacs.bioexcel.eu/t/group-water-and-ions-referenced-in-the-mdp-file-was-not-found-in-the-index-file/4383/1 "2022-06-29T09:58:06Z")

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GROMACS version:  
GROMACS modification: Yes/No  
Here post your question

 ![1](https://europe1.discourse-cdn.com/flex017/uploads/bioexcel1/original/2X/3/36849bf9b837cbd2745669ae977ab9d585bc9489.png)  
Here I am getting only 17 items in the list but this runs fine after that I used the command "gmx grompp -f nvt.mdp -c em.gro -r em.gro -p topol.top -n index.ndx -o nvt.tpr  
" which is throwing the error