# How to set up a system containing an acid molecule on air -water interface?

**URL:** <https://gromacs.bioexcel.eu/t/how-to-set-up-a-system-containing-an-acid-molecule-on-air-water-interface/4284>\
**Category:** User discussions\
**Tags:** simulation-setup\
**Created:** [June 9, 2022, 11:37am UTC](https://gromacs.bioexcel.eu/t/how-to-set-up-a-system-containing-an-acid-molecule-on-air-water-interface/4284 "2022-06-09T11:37:34Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Shivangi](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Shivangi](https://gromacs.bioexcel.eu/u/Shivangi)\
**Post date:** [June 9, 2022, 11:37am UTC](https://gromacs.bioexcel.eu/t/how-to-set-up-a-system-containing-an-acid-molecule-on-air-water-interface/4284/1 "2022-06-09T11:37:35Z")

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Hello everyone. I am very new to GROMACS and molecular dynamics in general and I want to simulate an acid at the water-vapor (or vacuum) interface. I am curious about how exactly can be set up this system.  
What I did,

1. Created a simulation box containing an air-water interface.
2. Minimized the energy of the system and equilibrated it.  
now i want to place an acid molecule on the interface.  
Can anyone please suggest me know how should I proceed?

Thank you.

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**Author:** ![keinerfan](https://avatars.discourse-cdn.com/v4/letter/k/e495f1/32.png) [@keinerfan](https://gromacs.bioexcel.eu/u/keinerfan)\
**Post date:** [January 9, 2024, 9:27am UTC](https://gromacs.bioexcel.eu/t/how-to-set-up-a-system-containing-an-acid-molecule-on-air-water-interface/4284/2 "2024-01-09T09:27:57Z")

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@Shivangi hello can you tell me how did you set your system up? and how do you generated air? is there any good reprenstation for air  
?