I'm trying to model a species for which the force field I'm using (OPLS-AA) doesn't contain all the force constants needed for some of the groups present. I've successfully defined several angle and dihedral force constants using quantum mechanical simulations to generate potential energy curves and I'm happy that the method works, however there are a few that I'm struggling with.
The specific dihedrals are adjacent ones between aromatic rings with a bridging atom between, e.g CA-CA-X-CA' and CA-X-CA'-CA', where the CA atoms are part of a phenyl ring and CA' atoms are in a napthyl group (Napth-X-Ph). It seems that there is a large amount of inter-dependence between the two dihedrals to the degree that the energy difference I'm trying to fit for one varies significantly with the value of the other angle. Fixing one dihedral at its most favourable angle and fitting the other (and vice-versa) results in a potential energy surface that is quite different to that obtained by quantum mechanics. Has anyone else managed to fit a similar system with strongly coupled dihedrals? Any suggestions or advice would be much appreciated! -- View this message in context: http://gromacs.5086.n6.nabble.com/Defining-strongly-interdependent-dihedral-force-constants-tp5002539.html Sent from the GROMACS Users Forum mailing list archive at Nabble.com. -- gmx-users mailing list gmx-users@gromacs.org http://lists.gromacs.org/mailman/listinfo/gmx-users * Please search the archive at http://www.gromacs.org/Support/Mailing_Lists/Search before posting! * Please don't post (un)subscribe requests to the list. Use the www interface or send it to gmx-users-requ...@gromacs.org. * Can't post? Read http://www.gromacs.org/Support/Mailing_Lists
