[gmx-users] User-Specified LJ Epsilon and Sigma

[Phwey Gil]

Hi,

I am looking to specify my own parameters for LJ parameters. Using the OPLS
forcefield, I only want to change the LJ parameters of some atoms.

I have H2O, C8H16O2 (Octanoic acid) and C2H6O (Ethanol).
I am using SPC/E for H2O, and OPLS for C8H16O2 and C2H6O. And I want to
change the LJ parameters for the hydrogens in C8H16O2 only.

I have tried specifying [ atomtypes ] in various places (In .top or .itp)
using the following format:

 [ atomtypes ]
      H     H      1.008      0.450     A       5.66387665E-4
2.80730518E-7

But I was not successful; I checked topol.tpr and the numbers are according
to OPLS and not my specified values.

Can someone give me advice on how to do this? I've checked the forums and I
was not successful at finding the correct information.

Best Regards,

Dan

-- 
Dan Gil
Case Western Reserve University | Class of 2016
Researcher, Department of Chemical Engineering
psg30 at case.edu