# Running Molecular Dyanamic Simulations with Dimers - No default Per. Imp. Dih. types

**URL:** <https://gromacs.bioexcel.eu/t/running-molecular-dyanamic-simulations-with-dimers-no-default-per-imp-dih-types/11583>\
**Category:** User discussions\
**Created:** [February 18, 2025, 12:33pm UTC](https://gromacs.bioexcel.eu/t/running-molecular-dyanamic-simulations-with-dimers-no-default-per-imp-dih-types/11583 "2025-02-18T12:33:11Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![NMRChem](https://avatars.discourse-cdn.com/v4/letter/n/85e7bf/32.png) [@NMRChem](https://gromacs.bioexcel.eu/u/NMRChem)\
**Post date:** [February 18, 2025, 12:33pm UTC](https://gromacs.bioexcel.eu/t/running-molecular-dyanamic-simulations-with-dimers-no-default-per-imp-dih-types/11583/1 "2025-02-18T12:33:11Z")

</div>

GROMACS version: GROMACS/2024.3-cpeAMD-24.03-rocm (2024.3, MPI)  
GROMACS modification: No  
I am having troubles simulating a dimer structure of my protein.

The monomer simulations run perfectly, and running the simulation of the monomer interacting with DNA run perfectly as well, but when I attempt to simulate a dimer of the structure, I get the error message:

gmx\_mpi editconf -f model.gro -d 0.8 -bt dodecahedron -o box.gro

ERROR 1 [file topol\_Protein\_chain\_A.itp, line 54193]:  
No default Per. Imp. Dih. types

ERROR 2 [file topol\_Protein\_chain\_A.itp, line 54497]:  
No default Per. Imp. Dih. types

ERROR 3 [file topol\_Protein\_chain\_B.itp, line 54193]:  
No default Per. Imp. Dih. types

ERROR 4 [file topol\_Protein\_chain\_B.itp, line 54497]:  
No default Per. Imp. Dih. types

How can I check this issue? Is there possibly something wrong with my PDB file? Where do I check the PDB to make sure the structures are coherent?

Here is the forcefield, just in case:

1: OL15 nucleic (Zgarbova et al., J. Chem. Theory Comput. 11, 5723-36, 2015

Thanks so much ahead of time,

M.