RM1 is a feature of MOPAC2012
MOPAC2012 is now available, free for academics, from http://openmopac.net.
If you qualify for Academic not-for-profit use request a password and download.
How to use RM1 in MOPAC2012:
Prepare an input data file and simply use the RM1 keyword, as shown in the next tab (.mop).