# Cutoff distance and PME as Coulombtype error

**URL:** <https://gromacs.bioexcel.eu/t/cutoff-distance-and-pme-as-coulombtype-error/8829>\
**Category:** User discussions\
**Created:** [April 9, 2024, 11:26am UTC](https://gromacs.bioexcel.eu/t/cutoff-distance-and-pme-as-coulombtype-error/8829 "2024-04-09T11:26:11Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![gromamk](https://avatars.discourse-cdn.com/v4/letter/g/b3f665/32.png) [@gromamk](https://gromacs.bioexcel.eu/u/gromamk)\
**Post date:** [April 9, 2024, 11:26am UTC](https://gromacs.bioexcel.eu/t/cutoff-distance-and-pme-as-coulombtype-error/8829/1 "2024-04-09T11:26:11Z")

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GROMACS version:2022.5-gcc-10.2.1  
GROMACS modification: Yes/No  
After minimizing the system energy, for calculating nvt, I faced with an error. If I set the coulombtype as PME, I receive the error **"The largest distance between excluded atoms is 0.810 nm, which is larger than the cut-off distance. This will lead to missing long-range corrections in the forces and energies**". While I increase the cut-off distance, I face with the error **“The cut-off length is longer than half the shortest box vector or longer than the smallest box diagonal element. Increase the box size or decrease rlist”**. But if I set the coulombtype as cut-off, everything goes well. The system includes Morse type bonding, too.

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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:** [April 9, 2024, 11:39am UTC](https://gromacs.bioexcel.eu/t/cutoff-distance-and-pme-as-coulombtype-error/8829/2 "2024-04-09T11:39:28Z")

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Do you expect that you can have excluded interactions at a distance 0.81 nm? That is quite long.

If your structure is correct than the proper solution is to use a (slightly) larger box.

Slighlty OT, but you seem to be using a very short cut-off distance. Have you checked that that is compatible with the force field?

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**Author:** ![gromamk](https://avatars.discourse-cdn.com/v4/letter/g/b3f665/32.png) [@gromamk](https://gromacs.bioexcel.eu/u/gromamk)\
**Post date:** [April 9, 2024, 12:15pm UTC](https://gromacs.bioexcel.eu/t/cutoff-distance-and-pme-as-coulombtype-error/8829/3 "2024-04-09T12:15:43Z")

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Thank for your response.

Indeed, I have just started to use the Gromacs and I am an amateur in it. When my cut-off (rvdw, rlist, rcoulomb) are set to 0.5 I receive the short cut-off error and If I increase them more then the 0.810, I face with the other error. I checked my topology file, it uses the “oplsaa.ff” force field. Moreover, I could not find any atoms (in bonds, angles, pairs, dihedrals and exclusions) mentioned in my topology file that have such distances. I changed my box size using the "editconf -box " command but this problem was not solved.