Dear all, I want to calculate the Tetrahedral order parameter through gmx. Can anyone help? Eventhough I tried but my system has 500 water molecules Fir that I am unable to make index file because it will take lots of time for typing any suggestions. Commend gmx order -f .xtc -s .tpr -b 0 -e 10000 -n .ndx -nr .ndx -d y -permolecule