Dear Gromacs Users, I am Simulating a RNA molecule using OPLS AA force field. I have written parameters using CHARMM27 force field for RNA molecules.
Minimising the molecule by invoking mdrun gives me the follwoing error. Energy minimization has stopped, but the forces have not converged to the requested precision Fmax < 1000 (which may not be possible for your system). It stopped because the algorithm tried to make a new step whose size was too small, or there was no change in the energy since last step. Either way, we regard the minimization as converged to within the available machine precision, given your starting configuration and EM parameters. Double precision normally gives you higher accuracy, but this is often not needed for preparing to run molecular dynamics. You might need to increase your constraint accuracy, or turn off constraints altogether (set constraints = none in mdp file) ----------------------------------------------------------------------------------------------------- The contents of the .mdp file are the following ; minim.mdp - used as input into grompp to generate em.tpr integrator = steep ; Algorithm (steep = steepest descent minimization) emtol = 1000.0 ; Stop minimization when the maximum force < 1000.0 kJ/mol/nm emstep = 0.01 ; Energy step size nsteps = 50000 ; Maximum number of (minimization) steps to perform ; Parameters describing how to find the neighbors of each atom and how to calculate the interactions nstlist = 1 ; Frequency to update the neighbor list and long range forces cutoff-scheme = Verlet ns_type = grid ; Method to determine neighbor list (simple, grid) coulombtype = PME ; Treatment of long range electrostatic interactions rcoulomb = 1.0 ; Short-range electrostatic cut-off rvdw = 1.0 ; Short-range Van der Waals cut-off pbc = xyz ; Periodic Boundary Conditions (yes/no) any suggestions ? *Anurag Dobhal* *Graduate Student (Bioprocess Technology)* *Institute of Chemical Technology, Mumbai* -- *DISCLAIMER:* *This communication is intended only for the person or entity to which it is addressed and may contain confidential and / or privileged material. Any review, retransmission, dissemination or other use is prohibited. If you have received this in error, please contact the sender and delete this material from your computer. Any comments or statements made herein do not necessarily reflect those of Nanomedicine Research Group. Before opening the email or accessing any attachments, please check and scan for virus.* -- Gromacs Users mailing list * Please search the archive at http://www.gromacs.org/Support/Mailing_Lists/GMX-Users_List before posting! * Can't post? Read http://www.gromacs.org/Support/Mailing_Lists * For (un)subscribe requests visit https://maillist.sys.kth.se/mailman/listinfo/gromacs.org_gmx-users or send a mail to gmx-users-requ...@gromacs.org.