OPLS-AA Force Field files

The purpose of this page is to highlight some key trends in the OPLS-AA force field bonded and non-bonded files. In particular to look at which non-bonded forces are the strongest or the weakest. This involves sorting various columns of ffnonbonded.itp and ffbonded.itp.

Suggestions for future pages:

-Computation of the LJ and Coulombic potentials for some commonly used opls types

-Computation of the LJ potentials and Coulombic potential functions from selection of two or more atom-types.

-Placing some newly published force field parameters into updated force field files (including how to apply these within the gromacs software- particularly in cases where the user does not have root access to the installer)

-Add several colums to atomtypes.atp. The first column would define the number of bonds the atom has to other atoms. (What is the maximum possible in the OPLS-AA field?) This will set the number of angles required to define the hybridizations state. The next five coulmns would define the bond order to each of the atoms (1=single, 2=double, 3=triple, 4=quadruple, 0=none). There are no quadruple bonded force field potentials in the OPLS-AA field to me knowledge. If there are less than 4/5 bonds, then zero is added. The next five columns will indicate the number of atoms bonded to each of the atoms the present atom is bonded to. This will set the number of dihedral options. These are required because even though a specific opls atom type apprears to be the best one for the job, it may fail grompp because it is missing an angle-type or dihedral-type.

Index to Key Pages
General OPLS-AA Topology Formatting

How to Use this Wikia

OPLS-AA Force Field Files

Draft Topologies

Accepted Best Working Topologies