# Solvent other than water **URL:** \ **Category:** User discussions\ **Created:** [December 25, 2023, 5:31pm UTC](https://gromacs.bioexcel.eu/t/solvent-other-than-water/7919 "2023-12-25T17:31:45Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![SP06](https://avatars.discourse-cdn.com/v4/letter/s/ecb155/32.png) [@SP06](https://gromacs.bioexcel.eu/u/SP06)\ **Post date:** [December 25, 2023, 5:31pm UTC](https://gromacs.bioexcel.eu/t/solvent-other-than-water/7919/1 "2023-12-25T17:31:45Z")
GROMACS version: 2021.4 GROMACS modification: Yes/No Here post your question : I want to simulate a system containing protein in a box of solvent (like ethanol or cyclohexane) . I am using OPLS-AA forcefield. I created the box around the protein using- gmx editconf -f 1AKI\_processed.gro -o 1AKI\_newbox.gro -c -d 1.0 -bt cubic Now how do I proceed for the next step of solvation where I need to fill the box with the solvent (say cyclohexane). Can anyone kindly help me with this ? ---
**Author:** ![milosz.wieczor](https://avatars.discourse-cdn.com/v4/letter/m/b19c9b/32.png) [@milosz.wieczor](https://gromacs.bioexcel.eu/u/milosz.wieczor)\ **Post date:** [December 27, 2023, 6:28pm UTC](https://gromacs.bioexcel.eu/t/solvent-other-than-water/7919/2 "2023-12-27T18:28:10Z")
`gmx insert-molecules` serves this purpose, use it with `-h` to see all its capabilities. ---
**Author:** ![SP06](https://avatars.discourse-cdn.com/v4/letter/s/ecb155/32.png) [@SP06](https://gromacs.bioexcel.eu/u/SP06)\ **Post date:** [December 28, 2023, 8:26am UTC](https://gromacs.bioexcel.eu/t/solvent-other-than-water/7919/3 "2023-12-28T08:26:24Z")
Can you please tell me the commands for the solvation steps with gmx insert? So there is no need of pre-equilibrated solvent box here? ---
**Author:** ![milosz.wieczor](https://avatars.discourse-cdn.com/v4/letter/m/b19c9b/32.png) [@milosz.wieczor](https://gromacs.bioexcel.eu/u/milosz.wieczor)\ **Post date:** [December 28, 2023, 12:04pm UTC](https://gromacs.bioexcel.eu/t/solvent-other-than-water/7919/4 "2023-12-28T12:04:12Z")
You can use a pre-equilibrated box with `gmx solvate`, or just insert a desired number of molecules with `gmx insert-molecules` (and then equilibrate the density/pressure). As per the help message, there’s just one obligatory input, `-ci` which is a structure file with your solvent molecule. You can then either set `-box X Y Z` to add to an empty box, or specify an existing structure with `-f` to add to. With `-nmol` you can set the max number of added solvent residues, and with `-ntry` you can say how many attempts to make if there’s overlap between an existing configuration and the new trial position. Many other options are probably irrelevant. Remember to have a separate `.itp` with the solvent’s topology, and to add the specified number of copies to your `.top` file - `gmx insert-molecules` doesn’t do that by default. ---
**Author:** ![SP06](https://avatars.discourse-cdn.com/v4/letter/s/ecb155/32.png) [@SP06](https://gromacs.bioexcel.eu/u/SP06)\ **Post date:** [December 31, 2023, 4:55am UTC](https://gromacs.bioexcel.eu/t/solvent-other-than-water/7919/5 "2023-12-31T04:55:51Z")
Thank you very much @milosz.wieczor ---
**Author:** ![scinikhil](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/scinikhil/32/3483_2.png) [@scinikhil](https://gromacs.bioexcel.eu/u/scinikhil)\ **Post date:** [December 31, 2023, 6:09pm UTC](https://gromacs.bioexcel.eu/t/solvent-other-than-water/7919/6 "2023-12-31T18:09:07Z")
Hi, I would suggest you to create a topology and structure of the solvent first. Then pass the topology to the main topology as itp file, then use gmx solvate to fill the box with new molecule. you may use `-cs structure_file.gro`