# Missing Harmonic Potential term when using more than 1 MPI rank

**URL:** <https://gromacs.bioexcel.eu/t/missing-harmonic-potential-term-when-using-more-than-1-mpi-rank/371>\
**Category:** User discussions\
**Created:** [June 24, 2020, 7:17pm UTC](https://gromacs.bioexcel.eu/t/missing-harmonic-potential-term-when-using-more-than-1-mpi-rank/371 "2020-06-24T19:17:00Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![minhho](https://avatars.discourse-cdn.com/v4/letter/m/7993a0/32.png) [@minhho](https://gromacs.bioexcel.eu/u/minhho)\
**Post date:** [June 24, 2020, 7:17pm UTC](https://gromacs.bioexcel.eu/t/missing-harmonic-potential-term-when-using-more-than-1-mpi-rank/371/1 "2020-06-24T19:17:00Z")

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GROMACS version:  
GROMACS modification: Yes/No

Dear Gromacs users,

I am experiencing a problem, which is when I run a simulation with 1 MPI rank, I have a harmonic potential term added in the energy calculation. However, when I try to run the same simulation with more than 1 MPI rank, I lost that harmonic potential term. This caused my ligand to not stay in the binding site of my protein even though I already applied some distance restrains on the ligand and some key residues. I would really appreciated if any one could help me with this.

Here is the link to google drive that contain md.log and .mdp:  
[https://drive.google.com/drive/folders/1WdaYxGDykcRx-SUsbCEslioSB7OCARVU?usp=sharing](https://drive.google.com/drive/folders/1WdaYxGDykcRx-SUsbCEslioSB7OCARVU?usp=sharing)

Thank you,  
Minh