Hi After I used grompp -f em.mdp -p topol.top -c solvated.gro -o em.tpr to collect my files into one em.tpr file (which is the meaning of gromp as fas as I understand it) Then I start mdrun for energy minimization with the command mdrun -nt 1 deffnm em and got the error Can not open file: topol.tpr What ist the problem? Thank you Greetings Lara