# How do I specify tail corrections for the traPPE force field?

**URL:** <https://gromacs.bioexcel.eu/t/how-do-i-specify-tail-corrections-for-the-trappe-force-field/738>\
**Category:** User discussions\
**Created:** [August 30, 2020, 10:15pm UTC](https://gromacs.bioexcel.eu/t/how-do-i-specify-tail-corrections-for-the-trappe-force-field/738 "2020-08-30T22:15:55Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![tfjermestad](https://avatars.discourse-cdn.com/v4/letter/t/9fc29f/32.png) [@tfjermestad](https://gromacs.bioexcel.eu/u/tfjermestad)\
**Post date:** [August 30, 2020, 10:15pm UTC](https://gromacs.bioexcel.eu/t/how-do-i-specify-tail-corrections-for-the-trappe-force-field/738/1 "2020-08-30T22:15:55Z")

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GROMACS version: 2020.3

My goal is to compute the self-diffusivity of methanol in the zeolite H-ZSM-5. I have started the first test simulations using the traPPE force field for methanol.

According to the traPPE web site ([http://trappe.oit.umn.edu/#param\_content](http://trappe.oit.umn.edu/#param_content)), simulations should be carried out with “analytic tail corrections for the Lennard-Jones Interactions”.  
How do I specify such tail corrections in Gromacs?

The system is the same as I described in this recent post:  
[How will using “vdwtype = Cut-off” instead of “vdwtype = pme” affect the results?](https://gromacs.bioexcel.eu/t/how-will-using-vdwtype-cut-off-instead-of-vdwtype-pme-affect-the-results/737)

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**Author:** ![jalemkul](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/jalemkul/32/18_2.png) [@jalemkul](https://gromacs.bioexcel.eu/u/jalemkul)\
**Post date:** [August 31, 2020, 2:11pm UTC](https://gromacs.bioexcel.eu/t/how-do-i-specify-tail-corrections-for-the-trappe-force-field/738/2 "2020-08-31T14:11:31Z")

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More specifically:

> LJ potentials are typically calculated using a site-site based spherical truncation at either 12 or 14 Å along with analytical tail corrections for the energy, pressure, and the chemical potential.

GROMACS supports such long-range corrections for energy and pressure (`DispCorr = EnerPres`) but has no ability to correct the chemical potential. Setting `rvdw` to 1.2 or 1.4 in concert with dispersion correction is the closest that GROMACS will get to being able to employ the force field as described.