Package: gromacs-openmpi

"gromacs-openmpi" package binaries on CentOS:

/usr/lib64/openmpi/bin/g_mdrun_openmpi /usr/lib64/openmpi/bin/g_mdrun_openmpi_d

You may install this package on CentOS with yum install gromacs-openmpi

"gromacs-openmpi" package binaries on Debian:

/usr/bin/mdrun_mpi_d.openmpi /usr/bin/mdrun_mpi.openmpi

You may install this package on Debian with apt-get install gromacs-openmpi