Dear lammps users,
I have came across a confusion regarding the pair_style lj/charmm variants
In the MacKerell paper (original charmm paper) the 12-6 format is eps*[(Rmin/rij)^12 - (Rmin/rij)^6] , as I think the Rmin=sig
In lammps, the potential is defined as
4eps[(sig/rij)^12 -(sig/rij)^6 ]
http://lammps.sandia.gov/doc/pair_charmm.html
this is while some other softwares yet define the potential as
eps*[(sig/rij)^12 - 2*(sig/rij)^6]
http://www.ks.uiuc.edu/Research/namd/2.9/ug/node22.html
could anyone make a comment on these
Thanks
FSE
charmm_MacKerell.pdf (308 KB)
Fatemesadat,
You can convert from one form to the other. See attached picture.
Jan-Michael
Fatemesadat,
You can convert from one form to the other. See attached picture.
Jan-Michael
Dear lammps users,
I have came across a confusion regarding the pair_style lj/charmm variants
In the MacKerell paper (original charmm paper) the 12-6 format is
eps*[(Rmin/rij)^12 - (Rmin/rij)^6] , as I think the Rmin=sig
this has to be a typo and Rmin != sigma
the CHARMM force field parameter files have in them:
V(Lennard-Jones) = Eps,i,j[(Rmin,i,j/ri,j)**12 - 2(Rmin,i,j/ri,j)**6]
jan-michael has already shown you how to interconvert these
based on the fact that Rmin = 2^(1/6) * sigma for a 12-6 LJ potential.
axel.