# How to obtain the double precision coordinate file as input for the normal mode analysis
**URL:** https://gromacs.bioexcel.eu/t/how-to-obtain-the-double-precision-coordinate-file-as-input-for-the-normal-mode-analysis/3951
**Category:** User discussions
**Tags:** analysis-tools
**Created:** [April 4, 2022, 3:32pm UTC](https://gromacs.bioexcel.eu/t/how-to-obtain-the-double-precision-coordinate-file-as-input-for-the-normal-mode-analysis/3951 "2022-04-04T15:32:42Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@zhiyiwu](https://gromacs.bioexcel.eu/u/zhiyiwu)
#### Post date: [April 4, 2022, 3:32pm UTC](https://gromacs.bioexcel.eu/t/how-to-obtain-the-double-precision-coordinate-file-as-input-for-the-normal-mode-analysis/3951/1 "2022-04-04T15:32:42Z")
I’m interested in using generating energy minimised coordinate file as input for the normal mode analysis.
However, it seems that I cannot get a gro file in the double precision format. I wonder if I can have some help, please? Thank you.
So I generate the em tpr file with
gmx\_d grompp -f minim.mdp -c lig.gro -p gas.top -maxwarn 1 -o em.tpr
Then run the em.
gmx\_d mdrun -o em.trr -s em.tpr
Then I tried to extract the double precision energy minimised coordinate from trr file to feed it as input for the normal mode analysis.
gmx\_d trjconv -f em.trr -o em.gro -dump 99999 -s em.tpr -ndec 32
However, it seems that the `em.gro` has the same single precision as usual despite the `-ndec 32`.
Later on I was thinking of using the `em.gro` as input to generate the normal mode analysis.
gmx\_d grompp -f nm.mdp -c em.gro -p gas.top -maxwarn 1 -o nm.tpr
Thanks.
GROMACS version: 2022
GROMACS modification: No
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### Author:  [@alevilla](https://gromacs.bioexcel.eu/u/alevilla)
#### Post date: [April 4, 2022, 4:34pm UTC](https://gromacs.bioexcel.eu/t/how-to-obtain-the-double-precision-coordinate-file-as-input-for-the-normal-mode-analysis/3951/2 "2022-04-04T16:34:06Z")
Hi,
Are you using mdrun to do normal mode analysis? Then, normal mode analysis is performed on the structure in the [tpr] file. For generating the run input file, one should use the minimized conformation from the full precision trajectory file trr, that should be possible using grompp with option -t .
I hope it works
\Alessandra
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### Author:  [@zhiyiwu](https://gromacs.bioexcel.eu/u/zhiyiwu)
#### Post date: [April 5, 2022, 9:35am UTC](https://gromacs.bioexcel.eu/t/how-to-obtain-the-double-precision-coordinate-file-as-input-for-the-normal-mode-analysis/3951/3 "2022-04-05T09:35:13Z")
Thanks. This solved my problem.