Negative Dihedral Constant

Hi All,

I noticed today that you could use a negative dihedral constant. For instance, if we use the charmm dihedral with n=1 and d=0, but change K to be either 1 or -1, then the “trans” state moves from 180 (K=1) to 0 (K=-1), also the potential energy shifts to the negative (K=-1). I was wondering if this is an OK method to shift the “trans” position since some force fields define “trans” as 0 while LAMMPS defines it as 180.


I don't know if you were waiting for someone else to reply. If so,
I apologize. Anyway, as you seem to know, the answer is yes. You can
change the angle where the minima occurs by using negative numbers for
K, if you want to do it that way.

If in doubt, try it and see.


(If it helps, here's a simple 4-particle data file named "" here:
I use this file along with "in.test" for testing dihedral angle
behavior in lammps.
By default, it is set to use "dihedral_style class2", but you can edit
the "in.test" file and change this to "dihedral_style charmm".)