[gmx-users] dihedral restraints

[David van der Spoel]

What should be the exact potential form for dihedral restraints?

If we define phi_ref as the reference angle and 2*dphi as the allowed
angular space we define 
phi' = (phi-phi_ref) MOD 360

then we have 

V = k/2 (phi' - dphi) ^2 (phi' > dphi)
V = k/2 (phi' - dphi) ^2 (phi' < dphi)
V = 0 (elsewhere)

Does that look right?
-- 
Groeten, David.
________________________________________________________________________
Dr. David van der Spoel, 	Biomedical center, Dept. of Biochemistry
Husargatan 3, Box 576,  	75123 Uppsala, Sweden
phone:	46 18 471 4205		fax: 46 18 511 755
spoel at xray.bmc.uu.se	spoel at gromacs.org   http://zorn.bmc.uu.se/~spoel
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