# Problem with "Distance between pull groups" and PBC

**URL:** <https://gromacs.bioexcel.eu/t/problem-with-distance-between-pull-groups-and-pbc/547>\
**Category:** User discussions\
**Created:** [July 21, 2020, 7:39pm UTC](https://gromacs.bioexcel.eu/t/problem-with-distance-between-pull-groups-and-pbc/547 "2020-07-21T19:39:02Z")\
**Posts on this page:** 1\
**Showing post:** 4

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**Author:** ![Ali](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/ali/32/170_2.png) [@Ali](https://gromacs.bioexcel.eu/u/Ali)\
**Post date:** [July 26, 2020, 11:41pm UTC](https://gromacs.bioexcel.eu/t/problem-with-distance-between-pull-groups-and-pbc/547/4 "2020-07-26T23:41:14Z")

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How could it be that they reached 6.186362 nm sooner that the previous (5.204208 nm)?  
what reaction coordinates are you using? can you upload your `.mdp` file? or only the `pull code` section.  
Nothing is random…

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