James W. Barnett jbarnet4@tulane.edu
This is a GROMACS implementation of the L-OPLS
modifications to the OPLS-AA force field. I have added the few
parameters that were changed in some if statements such that if you include
define = -DLOPLS in your mdp files, then the LOPLS parameters will be used for
those that have changed.
Note that the original atomtype numbers (prefixed
with opls_) can still be used, except for the methyl/methylene hydrogen
(opls_140). L-OPLS splits this up into two different atom types. In this case
opls_140A is the methyl hydrogen and opls_140B is the methylene hydrogen.
opls_140 is then just used in the case of methane hydrogens.
To install, place the oplsaa.ff folder where GROMACS can find it, like in
a directory pointed to by the environmental variable GMXLIB:
git clone git@github.com:wesbarnett/lopls.git
cd lopls
cp -r oplsaa.ff $GMXLIB/
Then include oplsaa.ff/forcefield.itp in your topology file as normal, except
add define = -DLOPLS to your mdp files when you want to use the modifications.
Additionally I've added TIP4P2005 and TIP4PEW water models to the force field directory.
If you use the L-OPLS parameters be sure to read and cite the following in addition to any OPLS papers:
- S. W. I. Siu, K. Pluhackova, and R. A. Bockmann. J. Chem. Theory Comp., 8, 4 (2012)
- K. Pluhackova, H. Morhenn, L. Lautner, W. Lohstroh, K. S. Nemkovski, T. Unruh, and R. A. Bockmann J. Phys. Chem. B. (2015
I've done my best in transcribing and converting the parameters for usage with GROMACS. That said, it is up to the user to ensure that the parameters are correct and that simulations are set up according to the methods presented in the papers above.