I was looking into the class2 potentials files. I wonder if there is small error in angle-class2.cpp. I am using Feb2014 Lammps version.
On lines 169 and 170 for terms aa1 and aa2, should there be a negative sign which comes from the -1/sin(x) term during the differentiation of the energy expression wrt to the angle?
I did not follow through with the rest of the code but I thought putting a negative sign there will be consistent with the convention used in this file and the rest of angle potential files.
Carnegie Mellon Uni