# Fatal erron in mdrun

**URL:** <https://gromacs.bioexcel.eu/t/fatal-erron-in-mdrun/11477>\
**Category:** User discussions\
**Created:** [February 6, 2025, 5:38am UTC](https://gromacs.bioexcel.eu/t/fatal-erron-in-mdrun/11477 "2025-02-06T05:38:01Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![samarth\_kittad](https://avatars.discourse-cdn.com/v4/letter/s/a698b9/32.png) [@samarth\_kittad](https://gromacs.bioexcel.eu/u/samarth_kittad)\
**Post date:** [February 6, 2025, 5:38am UTC](https://gromacs.bioexcel.eu/t/fatal-erron-in-mdrun/11477/1 "2025-02-06T05:38:01Z")

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

There is no domain decomposition for 16 ranks that is compatible with the  
given box and a minimum cell size of 4.00963 nm  
Change the number of ranks or mdrun option -rdd or -dds  
Look in the log file for details on the domain decomposition

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**Author:** ![samarth\_kittad](https://avatars.discourse-cdn.com/v4/letter/s/a698b9/32.png) [@samarth\_kittad](https://gromacs.bioexcel.eu/u/samarth_kittad)\
**Post date:** [February 6, 2025, 5:40am UTC](https://gromacs.bioexcel.eu/t/fatal-erron-in-mdrun/11477/2 "2025-02-06T05:40:11Z")

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help me solve this error please

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**Author:** ![al42and](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/al42and/32/1393_2.png) [@al42and](https://gromacs.bioexcel.eu/u/al42and)\
**Post date:** [February 6, 2025, 11:15am UTC](https://gromacs.bioexcel.eu/t/fatal-erron-in-mdrun/11477/3 "2025-02-06T11:15:54Z")

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Have you tried reducing the number of ranks? The problem is that your simulation box is too small to be split into 16 parts to be ran over 16 ranks.

You can read more about in the user guide: [Getting good performance from mdrun - GROMACS 2024.5 documentation](https://manual.gromacs.org/current/user-guide/mdrun-performance.html#running-mdrun-within-a-single-node)

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**Author:** ![samarth\_kittad](https://avatars.discourse-cdn.com/v4/letter/s/a698b9/32.png) [@samarth\_kittad](https://gromacs.bioexcel.eu/u/samarth_kittad)\
**Post date:** [February 10, 2025, 10:48am UTC](https://gromacs.bioexcel.eu/t/fatal-erron-in-mdrun/11477/4 "2025-02-10T10:48:29Z")

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can you please tell me the command for it

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<div class="post-metadata">

**Author:** ![al42and](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/al42and/32/1393_2.png) [@al42and](https://gromacs.bioexcel.eu/u/al42and)\
**Post date:** [February 10, 2025, 11:01am UTC](https://gromacs.bioexcel.eu/t/fatal-erron-in-mdrun/11477/5 "2025-02-10T11:01:57Z")

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It’s not a separate command, you just need to set correct mdrun flag. You can read more in the GROMACS documentation: [Getting good performance from mdrun - GROMACS 2024.5 documentation](https://manual.gromacs.org/current/user-guide/mdrun-performance.html#running-mdrun-within-a-single-node)