# Assemble a ternary system

**URL:** <https://gromacs.bioexcel.eu/t/assemble-a-ternary-system/1906>\
**Category:** User discussions\
**Created:** [April 6, 2021, 12:10pm UTC](https://gromacs.bioexcel.eu/t/assemble-a-ternary-system/1906 "2021-04-06T12:10:40Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![bellafrizzo](https://avatars.discourse-cdn.com/v4/letter/b/b487fb/32.png) [@bellafrizzo](https://gromacs.bioexcel.eu/u/bellafrizzo)\
**Post date:** [April 6, 2021, 12:10pm UTC](https://gromacs.bioexcel.eu/t/assemble-a-ternary-system/1906/1 "2021-04-06T12:10:40Z")

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Hello everyone,

I have two equilibrated boxes:  
The first one is just solvent (4 nm cubic box) as the second is a water+phosphate solution (5 nm cubic box)  
Is it possible to assemble them in such a way that I have a three stacked layer, namely solution/solvent/solution?  
Unfortunately, gmx solvate doesn’t allow for binary mixture solvation

Thank you in advance  
Matteo

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**Author:** ![jalemkul](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/jalemkul/32/18_2.png) [@jalemkul](https://gromacs.bioexcel.eu/u/jalemkul)\
**Post date:** [April 6, 2021, 12:53pm UTC](https://gromacs.bioexcel.eu/t/assemble-a-ternary-system/1906/2 "2021-04-06T12:53:45Z")

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See [Building Biphasic Systems](http://www.mdtutorials.com/gmx/biphasic/index.html) for a procedure. You can’t combine boxes of different dimensions, so your solvent box needs to be 5 nm to match your solution box.

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<div class="post-metadata">

**Author:** ![bellafrizzo](https://avatars.discourse-cdn.com/v4/letter/b/b487fb/32.png) [@bellafrizzo](https://gromacs.bioexcel.eu/u/bellafrizzo)\
**Post date:** [April 6, 2021, 1:09pm UTC](https://gromacs.bioexcel.eu/t/assemble-a-ternary-system/1906/3 "2021-04-06T13:09:23Z")

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Hi Justin,

So I can double the size along z of my solution box and then solvate with the solvent if they match in dimensions?

Matteo

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**Author:** ![jalemkul](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/jalemkul/32/18_2.png) [@jalemkul](https://gromacs.bioexcel.eu/u/jalemkul)\
**Post date:** [April 6, 2021, 1:27pm UTC](https://gromacs.bioexcel.eu/t/assemble-a-ternary-system/1906/4 "2021-04-06T13:27:41Z")

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Yes, that’s right.