[gmx-users] negative dihedral cp (during cgenff conversion)

Peter C. Lai pcl at uab.edu
Mon Aug 15 02:50:35 CEST 2011

Random noob question:
Should the cp field (field 7) in [ dihedraltypes ] always be positive or can
it be negative? 

In the CGenFF conversion, the CHARMM dihedral has:

OG302  CG2O2  CG321  CG331     -0.1500  1   180.00 ! LIPID methyl proprionate
when I convert to gromacs:

[ dihedraltypes ]
; i     j       k       l       func    phi0    cp      mult
OG302  CG2O2  CG321  CG331      9       180.0   -0.62760    1 ;LIPID methyl prop 

This is the only instance I have seen of a negative number for the dihedral
term, so I wonder what the right way to handle it is...
(I suppose I could just run it and see...)
Peter C. Lai			| University of Alabama-Birmingham
Programmer/Analyst		| BEC 257
Genetics, Div. of Research	| 1150 10th Avenue South
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