# Will vdw cutoffs in the mdp file affect my user-defined interactions?

**URL:** <https://gromacs.bioexcel.eu/t/will-vdw-cutoffs-in-the-mdp-file-affect-my-user-defined-interactions/2447>\
**Category:** User discussions\
**Tags:** forcefield, mdp-parameters\
**Created:** [July 2, 2021, 10:16pm UTC](https://gromacs.bioexcel.eu/t/will-vdw-cutoffs-in-the-mdp-file-affect-my-user-defined-interactions/2447 "2021-07-02T22:16:27Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![rmera](https://avatars.discourse-cdn.com/v4/letter/r/a3d4f5/32.png) [@rmera](https://gromacs.bioexcel.eu/u/rmera)\
**Post date:** [July 2, 2021, 10:16pm UTC](https://gromacs.bioexcel.eu/t/will-vdw-cutoffs-in-the-mdp-file-affect-my-user-defined-interactions/2447/1 "2021-07-02T22:16:27Z")

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GROMACS version: 2021.X  
GROMACS modification: No

Say I define a series of custom Lennard-Jones potentials in my itp, using the “[pairs]” section.  
Then, in my mdp file, I add the following:

vdw\_type = cutoff  
vdw-modifier = Potential-shift-verlet  
rvdw = 1.1

Will my custom [pairs] potentials also be affected by the vdw modifications in the mdp?

Thanks!

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**Author:** ![alevilla](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/alevilla/32/439_2.png) [@alevilla](https://gromacs.bioexcel.eu/u/alevilla)\
**Post date:** [July 6, 2021, 12:51pm UTC](https://gromacs.bioexcel.eu/t/will-vdw-cutoffs-in-the-mdp-file-affect-my-user-defined-interactions/2447/2 "2021-07-06T12:51:21Z")

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Hi,  
I think that the mdp setting acts on the nonbonded interactions, not on the pairs interaction.  
It is always good to check new implement parameters and settting using a simplify case  
Best regards  
Alessandra