# Atomtype hn was defined previously (e.g. in the forcefield files), and has now been defined again

**URL:** <https://gromacs.bioexcel.eu/t/atomtype-hn-was-defined-previously-e-g-in-the-forcefield-files-and-has-now-been-defined-again/6634>\
**Category:** User discussions\
**Tags:** forcefield, grompp\
**Created:** [June 19, 2023, 1:55pm UTC](https://gromacs.bioexcel.eu/t/atomtype-hn-was-defined-previously-e-g-in-the-forcefield-files-and-has-now-been-defined-again/6634 "2023-06-19T13:55:58Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Dipayansarder](https://avatars.discourse-cdn.com/v4/letter/d/d26b3c/32.png) [@Dipayansarder](https://gromacs.bioexcel.eu/u/Dipayansarder)\
**Post date:** [June 19, 2023, 1:55pm UTC](https://gromacs.bioexcel.eu/t/atomtype-hn-was-defined-previously-e-g-in-the-forcefield-files-and-has-now-been-defined-again/6634/1 "2023-06-19T13:55:59Z")

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GROMACS version: 2020.4  
GROMACS modification: No  
While executing gmx\_mpi grompp command ionic liquid system I am getting the following warning.

```auto
WARNING 1 [file ETA_nonbonded.itp, line 5]:
  Atomtype hn was defined previously (e.g. in the forcefield files), and
  has now been defined again. This could happen e.g. if you would use a
  self-contained molecule .itp file that duplicates or replaces the
  contents of the standard force-field files. You should check the contents
  of your files and remove such repetition. If you know you should override
  the previous definition, then you could choose to suppress this warning
  with -maxwarn.

WARNING 2 [file ETA_nonbonded.itp, line 6]:
  Atomtype c3 was defined previously (e.g. in the forcefield files), and
  has now been defined again. This could happen e.g. if you would use a
  self-contained molecule .itp file that duplicates or replaces the
  contents of the standard force-field files. You should check the contents
  of your files and remove such repetition. If you know you should override
  the previous definition, then you could choose to suppress this warning
  with -maxwarn.

WARNING 3 [file ETA_nonbonded.itp, line 9]:
  Atomtype h1 was defined previously (e.g. in the forcefield files), and
  has now been defined again. This could happen e.g. if you would use a
  self-contained molecule .itp file that duplicates or replaces the
  contents of the standard force-field files. You should check the contents
  of your files and remove such repetition. If you know you should override
  the previous definition, then you could choose to suppress this warning
  with -maxwarn.

Can this warning be ignored? Could anyone suggest how to resolve the problem?
```

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<div class="post-metadata">

**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:** [June 22, 2023, 1:44pm UTC](https://gromacs.bioexcel.eu/t/atomtype-hn-was-defined-previously-e-g-in-the-forcefield-files-and-has-now-been-defined-again/6634/2 "2023-06-22T13:44:13Z")

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You should check where those duplicate definitions are. If the parameter values are identical, there is no issue and you can ignore the warning. If the values differ, you need to find out which values are correct.