Fig. 1
From: Accuracy evaluation and addition of improved dihedral parameters for the MMFF94s
Example representations of torsion fragments. Example 1 refers to the dihedral angle of the rotation around a C–C bond, whereas C1 is part of a delocalized system, neighboring two C-atoms with two neighbors each (n2C). C2 is a non-aromatic C (!aC) bound to a nitrogen atom. In example 2, we again refer to the rotation around a C1–C2 bond. C1 is a non-aromatic carbon, bound to a non-aromatic carbon with less than 4 neighboring atoms (C!a,n<4; sp2 or sp hybridized). C2 is an amide carbonyl carbon. Example 3 is a combination of Examples 1 and 2, where C1 is part of a delocalized system, neighboring two Cn2 atoms, and C2 is an amide carbonyl carbon