[gmx-users] opls parameters

[Dongsheng Zhang]

Dear Mark,

I think C2 is CH2 group, rather than N atom because of its mass (refer
to opls_071, opls_072), and it is said in ffoplsaa.atp that types 1-134
are from the united-atom OPLS.

Dongsheng



On Sun, 2006-12-03 at 17:20 +1100, Mark Abraham wrote:
> > Sorry i'm probably being a bit slow, but i can't see where the "bond-type"
> > atom names/types don't correspond with the opls-xxx names from the
> > ffoplsbon.atp and ffoplsbon.rtp files for use with the ffoplsbon.itp file
> > names.
> 
> The header for ffoplsaanb.itp is
> 
> [ atomtypes ]
> ; full atom descriptions are available in ffoplsaa.atp
> ; name  bond_type    mass    charge   ptype          sigma      epsilon
>  opls_001   C   6      12.01100     0.500       A    3.75000e-01 
> 4.39320e-01 ; SIG
>  opls_002   O   8      15.99940    -0.500       A    2.96000e-01 
> 8.78640e-01 ; SIG
>  opls_003   N   7      14.00670    -0.570       A    3.25000e-01 
> 7.11280e-01 ; SIG
>  opls_004   H   1       1.00800     0.370       A    0.00000e+00  0.00000e+00
>  opls_005   C2  6      14.02700     0.200       A    3.80000e-01 
> 4.93712e-01 ; SIG
> 
> The header for ffoplsaa.atp is
> 
>  opls_001   12.01100  ;
>  opls_002   15.99940  ;
>  opls_003   14.00670  ;
>  opls_004    1.00800  ;
>  opls_005   14.02700  ;
> 
> So evidently opls_005 is a nitrogen atom... so what's with the "C2  6"?
> Further, there is no bonded interaction in ffoplsaa.rtp for "C2", but
> there is C_2... So I really don't understand what is going on.
> 
> Mark
> 
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