Helplamps, after entering the command, the unknown option: -D is always displayed.

Personally, I think your problem should be that the environment variable is not set.

You can use the command set path = d: \ mpich2 \ bin; % Add the path of the environment variable.

Then put the CD into the directory where your in.friction file is located (be careful to copy the executable file lmp_win_mpi to this directory), and then run it.

MPI exec-n 2 LMP _ win _ MPI & lt； internal friction

I hope it helps you.