Two different ways to define the orientation, i.e. two different sets of angles.
The first way is the only one used in solid mechanics, the angles are noted (ψ,θ,φ). In materials sciences, Bunge, who is one of the reference in crystallite orientation, uses different names: (φ1
). Additionally, he defines the orientation with another variant of Euler angles where the second rotation is performed around the new y-axis; these angles ares called (Ψ,Θ,Φ), although they are totally different from the angles named with the lower-case version of the same greek letters.