# Change of Simulation Box shape

**URL:** <https://gromacs.bioexcel.eu/t/change-of-simulation-box-shape/2344>\
**Category:** User discussions\
**Created:** [June 10, 2021, 5:38pm UTC](https://gromacs.bioexcel.eu/t/change-of-simulation-box-shape/2344 "2021-06-10T17:38:07Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![amnah](https://avatars.discourse-cdn.com/v4/letter/a/8e7dd6/32.png) [@amnah](https://gromacs.bioexcel.eu/u/amnah)\
**Post date:** [June 10, 2021, 5:38pm UTC](https://gromacs.bioexcel.eu/t/change-of-simulation-box-shape/2344/1 "2021-06-10T17:38:07Z")

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GROMACS version:2020  
GROMACS modification: Yes/No  
Here post your question

Hi all,

I am currently running a long simulation but I would like to change the box shape (From triclinic to cubic) . Can I finish this simulation and then change the box shape and continue the simulation from the current time point to continue the run or I need to start from time 0?. Is there any GROMASC option I can use to change the dimension of the box from triclinic to a cubic or orthorhombic box? Any suggestions would be highly appreciated.

Thank you so much

Amnah

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**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:** [June 15, 2021, 8:55am UTC](https://gromacs.bioexcel.eu/t/change-of-simulation-box-shape/2344/2 "2021-06-15T08:55:35Z")

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Hi,  
usually reshaping a box may require also partial re-solvation of the box and a change in the phase space, thus the simulation will start from t=0.  
Then in the analyze you can consider both simulation separately.  
Best regards  
Alessandra

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<div class="post-metadata">

**Author:** ![amnah](https://avatars.discourse-cdn.com/v4/letter/a/8e7dd6/32.png) [@amnah](https://gromacs.bioexcel.eu/u/amnah)\
**Post date:** [June 15, 2021, 11:22am UTC](https://gromacs.bioexcel.eu/t/change-of-simulation-box-shape/2344/3 "2021-06-15T11:22:49Z")

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@alevilla  
Thank you so much Alessandra for replying!  
The problem is I already ran the simulation for 2us which took us so long! so there is no way to continue the simulation from the last time point after re-shaping the box?

I have been advised to use the following commands :  
gmx editconf -f your\_system.gro -o new\_cubic\_system.gro -bt cubic  
then  
grompp specifying  
-c new\_cubic\_system.gro -r new\_cubic\_system.gro -t previous\_geometry\_checkpoint.cpt

Any suggestions would be greatly appreciated.

Amnah