# Umbrella sampling box size error

**URL:** <https://gromacs.bioexcel.eu/t/umbrella-sampling-box-size-error/2972>\
**Category:** User discussions\
**Tags:** umbrella-sampling\
**Created:** [October 17, 2021, 1:23pm UTC](https://gromacs.bioexcel.eu/t/umbrella-sampling-box-size-error/2972 "2021-10-17T13:23:11Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![varun.kesherwani](https://avatars.discourse-cdn.com/v4/letter/v/f1d935/32.png) [@varun.kesherwani](https://gromacs.bioexcel.eu/u/varun.kesherwani)\
**Post date:** [October 17, 2021, 1:23pm UTC](https://gromacs.bioexcel.eu/t/umbrella-sampling-box-size-error/2972/1 "2021-10-17T13:23:11Z")

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Hello Everyone,

I am trying to run my peptide for umbrella sampling. Pulling in the Z direction.

Box size is below

gmx editconf -f seq1.X.gro -o seq1.X-newbox.gro -center 3.280 3.281 5.7965 -box 6.41840 6.44350 8.7965

gmx editconf -f seq1.X.gro -o seq1.X-newbox.gro -center 3.280 3.281 5.7965 -box 6.41840 6.44350 10.7965

I do not know why I am getting the same message even I changed my box Z coordinate from 8.7965 to 10.7965. Any Suggestion.

Distance between pull groups 1 and 2 (3.475811 nm) is larger than 0.49 times the box size (3.475776).

Distance between pull groups 1 and 2 (3.409405 nm) is larger than 0.49 times  
the box size (3.409306).

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<div class="post-metadata">

**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:** [October 18, 2021, 3:27pm UTC](https://gromacs.bioexcel.eu/t/umbrella-sampling-box-size-error/2972/2 "2021-10-18T15:27:02Z")

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Hi,

> [@varun.kesherwani](#):
>
> do not know why I am getting the same message even I changed my box Z coordinate from 8.7965 to 10.7965. Any Suggestion.

When the box size is compared with the distance, the smaller size is of the box considered. It is a guess from the information that you reported.

\Alessandra