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<DIV><FONT face=Arial size=2>Hi,</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>I'm trying to put together a topology for a
nicotine analogue molecule using the OPLS forcefield.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Most of the atom types that I need and the force
field parameters are already in the OPLS force field, except for a couple of
dihedrals. So, I ran a series of single point calculations using Gaussian98 to
get the energies of the configuration with the dihedral angles changing from 0
to 360, and am attempting to get the dihedral coefficients by a least-squares
fitting to the Ryckaert-Bellemans potential function. Is this a good way to
get the dihedral parameters? I'm using the optimized geometry I get from
Gaussian, and am just changing the dihedral angles.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>The second question is, in the manual it's
stated that, with the RB potential, the 1-4 interactions must be excluded, is
this also the case when you're using the OPLS force field? And should I also
exclude the 1-4 interactions when I'm using the parameters derived as above?
</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Thanks for your help in advance!</FONT></DIV>
<DIV><FONT face=Arial size=2>Jee.</FONT></DIV></BODY></HTML>