# How to decompose enthalpic components using the group energy exclusion scheme?

**URL:** <https://gromacs.bioexcel.eu/t/how-to-decompose-enthalpic-components-using-the-group-energy-exclusion-scheme/1728>\
**Category:** User discussions\
**Created:** [March 10, 2021, 12:47pm UTC](https://gromacs.bioexcel.eu/t/how-to-decompose-enthalpic-components-using-the-group-energy-exclusion-scheme/1728 "2021-03-10T12:47:26Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Albin](https://avatars.discourse-cdn.com/v4/letter/a/6de8d8/32.png) [@Albin](https://gromacs.bioexcel.eu/u/Albin)\
**Post date:** [March 10, 2021, 12:47pm UTC](https://gromacs.bioexcel.eu/t/how-to-decompose-enthalpic-components-using-the-group-energy-exclusion-scheme/1728/1 "2021-03-10T12:47:26Z")

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GROMACS version:2019.4  
GROMACS modification: No  
Hello I am studying the unfolding process of a protein using REMD and I need to decompose the enthalpic contribution (as well as the entropic contribution) of protein and water from the whole system enthalpy. How can I do it in Gromacs?  
I already generated a 500ns trajectory for all 48 replicas of my system.

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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:** [March 18, 2021, 3:18pm UTC](https://gromacs.bioexcel.eu/t/how-to-decompose-enthalpic-components-using-the-group-energy-exclusion-scheme/1728/2 "2021-03-18T15:18:47Z")

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With PME, which I guess you are using, you can not decompose enthalpic components. As far as I know you can never decompose entropic components, except for simple cases such as a binary mixture of liquids.

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**Author:** ![Albin](https://avatars.discourse-cdn.com/v4/letter/a/6de8d8/32.png) [@Albin](https://gromacs.bioexcel.eu/u/Albin)\
**Post date:** [March 29, 2021, 6:24pm UTC](https://gromacs.bioexcel.eu/t/how-to-decompose-enthalpic-components-using-the-group-energy-exclusion-scheme/1728/3 "2021-03-29T18:24:46Z")

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Thanks, Hess for the reply.  
Yes, I am using PME and can I decompose enthalpy terms by using the “energygrp-excl” keyword in md rerun. I don’t know much about how to use it.

Also, can I use something other than PME while doing rerun.

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<div class="post-metadata">

**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:** [April 6, 2021, 2:35pm UTC](https://gromacs.bioexcel.eu/t/how-to-decompose-enthalpic-components-using-the-group-energy-exclusion-scheme/1728/4 "2021-04-06T14:35:26Z")

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You can not decompose energies with PME.