[gmx-users] opls dihedral function
Frauke Meyer
fmeyer at iris3.simm.ac.cn
Fri Nov 12 09:10:31 CET 2004
Hi,
I am trying to figure out how the parameters for OPLS dihedrals
are set and are confused about the different protein/polymer
conventions.
Parameters V_1 and V_3 of the opls dihedral potential are zero
for dihedrals of flat groups like in aromatic rings.
For these cases V_0 is positive and V_2 = -V_0
Thus the function is simply
V = V_0 - V_0 (1 - cos(2phi)) (see eq 4.59 in the manual)
= V_0 cos(2phi)
But this gives maxima for phi=0 and phi=180 (V=V_0) and mimima
for phi=90 and phi=270 (V=-V0). Shouldn't it be vice versa?
Confused
Frauke
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