Is MMFP actually supported with OpenMM?
Using the latest version of OpenMM, it doesn't appear to be:
***** LEVEL -1 WARNING FROM *****
***** Number of atoms in restraint too large/geometric shape not supported
Where the MMFP block generated by CHARMM-GUI applying a restraint to non-waters looks like this:
GEO rcm sphere -
Xref @xcen Yref @ycen Zref @zcen XDIR 1.0 YDIR 1.0 ZDIR 1.0 -
harmonic FORCE 1.0 select .not. ( hydrogen .or. resname TIP3 .or. segid @posid .or. segid @negid ) end
My system is a small peptide system (12 AA's) so I doubt size is the issue. When run on CPUs, the peptide is nicely centred in the water box. Commenting out the block means the simulation runs using OpenMM acceleration but the peptide flaps around outside the centred water box.
I note in a more recent post ( CHARMM Forum | How to maintain plane orientation
), the suggestion of CONS HARM ABSO
as the solution.
So, if I wanted to apply a harmonic constraint as per the manual CONS
to mimic effect of the MMFP block, perhaps something like this would do?
CONS HARM ABSO 1.0 FORCE 1.0 SELE .not. ( hydrogen .or. resname TIP3 .or. segid @posid .or. segid @negid ) END COMP