# Trajectory file conversion

**URL:** <https://gromacs.bioexcel.eu/t/trajectory-file-conversion/9975>\
**Category:** User discussions\
**Created:** [August 24, 2024, 4:23pm UTC](https://gromacs.bioexcel.eu/t/trajectory-file-conversion/9975 "2024-08-24T16:23:57Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Sounak\_Biswas](https://avatars.discourse-cdn.com/v4/letter/s/3ec8ea/32.png) [@Sounak\_Biswas](https://gromacs.bioexcel.eu/u/Sounak_Biswas)\
**Post date:** [August 24, 2024, 4:23pm UTC](https://gromacs.bioexcel.eu/t/trajectory-file-conversion/9975/1 "2024-08-24T16:23:57Z")

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GROMACS version: 2023.3  
GROMACS modification: Yes/No  
I have run the md simulation on Gromacs version 2023.3. Using the obtained .tpr .xtc .top file i have tried to run mmpbsa calculation but it always show me error. Is there any way so that i can convert the format of .tpr .xtc .top output file of Gromacs version 2023.3 to the format of output files obtained from Gromacs version 2021 ?

I have run the following command for mmpbsa calculation:

mpirun -np 4 gmx\_MMPBSA -O -i mmpbsa.in -cs NPT-MD.tpr -ci index.ndx -cg 1 13 -ct 30ns.xtc -cp topol.top

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**Author:** ![obZehn](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/obzehn/32/2629_2.png) [@obZehn](https://gromacs.bioexcel.eu/u/obZehn)\
**Post date:** [August 24, 2024, 4:53pm UTC](https://gromacs.bioexcel.eu/t/trajectory-file-conversion/9975/2 "2024-08-24T16:53:30Z")

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Ideally .xtc and .top file should already work with the older GROMACS version, most of the times at least. The problem is the .tpr file. The best you can do is to re-run the command to generate the .tpr file but with the GROMACS version you want sourced, so that you get the .tpr of the correct version, and then run the analysis with the new .tpr file!