[gmx-users] Lennard Jones Parameters for Ammonia in ffoplsaa

Mark Abraham Mark.Abraham at anu.edu.au
Mon Oct 19 10:07:22 CEST 2009

Darrell Koskinen wrote:
> Hi,
> I see that the Lennard Jones parameters for the N & H atoms in ammonia, 
> represented by opls_127 and opls_128 in the file ffoplsaanb.itp are:
> opls_127   NT  7     14.00670    -1.020       A    3.42000e-01  7.11280e-01
> opls_128   H   1       1.00800     0.340       A    0.00000e+00  
> 0.00000e+00
> Why are sigma and epsilon both zero for H? Are the LJ parameters for H 
> embedded in the parameter for NT? If so, how were these parameters 
> combined?

What do other H have? What do the OPLS-AA paper(s) have to say about 
such H atoms?


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