# In solvation step, method to control distance between water molecules

**URL:** <https://gromacs.bioexcel.eu/t/in-solvation-step-method-to-control-distance-between-water-molecules/7102>\
**Category:** User discussions\
**Created:** [August 30, 2023, 7:38am UTC](https://gromacs.bioexcel.eu/t/in-solvation-step-method-to-control-distance-between-water-molecules/7102 "2023-08-30T07:38:48Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![HyewonLee](https://avatars.discourse-cdn.com/v4/letter/h/6a8cbe/32.png) [@HyewonLee](https://gromacs.bioexcel.eu/u/HyewonLee)\
**Post date:** [August 30, 2023, 7:38am UTC](https://gromacs.bioexcel.eu/t/in-solvation-step-method-to-control-distance-between-water-molecules/7102/1 "2023-08-30T07:38:48Z")

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GROMACS version: 2023.2  
GROMACS modification: Yes/No

In solvation(just adding water molecules), after adding pbc box around the system, is there any method to control distance between water molecules?

gmx editconf -f pro.gro -o box.gro -c -d 1.7 -bt cubic  
gmx solvate -cp box.gro -cs spc216.gro -o solv.gro -p topol.top

I’m using these commands now. How I modify?  
I want the water molecules to be more densely packed inside the box.

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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:** [September 1, 2023, 8:39am UTC](https://gromacs.bioexcel.eu/t/in-solvation-step-method-to-control-distance-between-water-molecules/7102/2 "2023-09-01T08:39:56Z")

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Hi,  
The configuration of the solvent is defined the option -cs. The file spc216.gro is a water box equilibrated using SPC water molecules. You can also other solvents box, just by providing your solvent gro file to the option -cs.  
see more here [https://manual.gromacs.org/current/onlinehelp/gmx-solvate.html#gmx-solvate](https://manual.gromacs.org/current/onlinehelp/gmx-solvate.html#gmx-solvate)  
\Alessandra