How to obtain the double precision coordinate file as input for the normal mode analysis

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 -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 -maxwarn 1 -o nm.tpr

GROMACS version: 2022
GROMACS modification: No


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

Thanks. This solved my problem.