# How to calculate long-range interactions using GROMACS?

**URL:** <https://gromacs.bioexcel.eu/t/how-to-calculate-long-range-interactions-using-gromacs/11028>\
**Category:** User discussions\
**Tags:** analysis-tools\
**Created:** [January 14, 2025, 9:21am UTC](https://gromacs.bioexcel.eu/t/how-to-calculate-long-range-interactions-using-gromacs/11028 "2025-01-14T09:21:52Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![subhadip](https://avatars.discourse-cdn.com/v4/letter/s/3d9bf3/32.png) [@subhadip](https://gromacs.bioexcel.eu/u/subhadip)\
**Post date:** [January 14, 2025, 9:21am UTC](https://gromacs.bioexcel.eu/t/how-to-calculate-long-range-interactions-using-gromacs/11028/1 "2025-01-14T09:21:52Z")

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GROMACS version: 2022.3  
GROMACS modification: No  
gmx energy module can be used to calculate short-range LJ and coulomb interactions between molecules. Is there any way to obtain long-range corrections using GROMACS?

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**Author:** ![hess](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/hess/32/416_2.png) [@hess](https://gromacs.bioexcel.eu/u/hess)\
**Post date:** [January 15, 2025, 6:57pm UTC](https://gromacs.bioexcel.eu/t/how-to-calculate-long-range-interactions-using-gromacs/11028/2 "2025-01-15T18:57:02Z")

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gmx energy does not calculate energies, mdrun does that. Long-range Coulomb interactions are difficult to decompose. And even if you would, the results are rather meaningless in most cases, as there is strong coupling of electrostatic interactions between different molecules, in particular between molecules and solvent.

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**Author:** ![subhadip](https://avatars.discourse-cdn.com/v4/letter/s/3d9bf3/32.png) [@subhadip](https://gromacs.bioexcel.eu/u/subhadip)\
**Post date:** [January 16, 2025, 9:41am UTC](https://gromacs.bioexcel.eu/t/how-to-calculate-long-range-interactions-using-gromacs/11028/3 "2025-01-16T09:41:33Z")

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@hess Thank you for the answer. Let me rephrase my question.  
I want to calculate interaction energy between two molecules. I can calculate that using mdrun by defining energy groups in my input script. gmx energy module now can be used to extract short ranged coulomb and LJ interaction energies between the molecules. My questions are.

1. Can I obtain long-range electrostatic interactions between two molecules?
2. Can I get dispersion correction for LJ interaction between two molecules, given DispCorr is set to EnerPres/Ener in the input script?

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**Author:** ![hess](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/hess/32/416_2.png) [@hess](https://gromacs.bioexcel.eu/u/hess)\
**Post date:** [January 28, 2025, 11:34am UTC](https://gromacs.bioexcel.eu/t/how-to-calculate-long-range-interactions-using-gromacs/11028/4 "2025-01-28T11:34:33Z")

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My previous answer is still valid.