[gmx-users] OPLS force field issue

Mary Mary.Less at gmx.de
Thu Apr 30 12:45:11 CEST 2015

Dear gmx users, 

I also try to use the OPLS force field for my simulations. After defining
suitable atomtypes:

opls_110 (type C2)
opls_071 (type C2)

I would like to add the suitable bondtypes, angletypes and so on. But where
do I get those parameters for the angles and k? 

I thought, that the values have to be in the ffbonded.itp.

If I am interested in opls_182 for example, which has the bond type CT (I
got this information from the atomtypes.atp) I found several informations
about CT in the ffbonded: 

[ bondtypes ]
; i    j  func       b0          kb
CT    CT      1    0.15290   224262.4   ; CHARMM 22 parameter file

[ angletypes ]
;  i    j    k  func       th0       cth
CT     CT     CT      1   112.700    488.273   ; CHARMM 22 parameter file

But there are no parameters listet for C2. 
I know that I could also "ignore" the parameters and include the oplsaa.ff
in my topology file but is there also a way to get those parameters directly? 

I suppose there is a way, as I found various posts including this 
parameters as for example in this post. 

(".....>   C2    C3       1    0.16020   292880.0   ;..... )"

Many thanks in advance!


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