[gmx-users] Lennard-Jones Parameters in ffnonbonded.itp

[Lara Bunte]

Hello
I use a charmm force field in gromacs. I almost finished my parametrization except for Lennard-Jones parameters. For this parameters I want to adopt the values in the charmm force field for the basic atom types. 

In gromacs I have to put this parameters in the ffnonbonded.itp file in the section [ pairtypes ] and I have to give following informations: 

; i     j       func    sigma1-4        epsilon1-4 ; THESE ARE 1-4 INTERACTIONS

in example

CP1     CP1     1       0.338541512893  0.04184

Now here is a section of information given in the charmm documentation. 

!V(Lennard-Jones) = Eps,i,j[(Rmin,i,j/ri,j)**12 - 2(Rmin,i,j/ri,j)**6]
!
!epsilon: kcal/mole, Eps,i,j = sqrt(eps,i * eps,j)
!Rmin/2: A, Rmin,i,j = Rmin/2,i + Rmin/2,j
!
!atom  ignored    epsilon      Rmin/2   ignored   eps,1-4       Rmin/2,1-4
!
HN1      0.0       -0.0460    0.2245 
HN2      0.0       -0.0460    0.2245 


The question is: 


How to adopt the values in the charmm force field for the basic atom types in gromacs? I do not really know what I have to write in the [ pairtypes ] section in gromacs. 


Thank you for helping me
Greetings
Lara