where g and h are the norms of the orthogonalized energy difference gradient and derivative coupling vector, respectively. The magnitudes of the s x and s y parameters characterize the tilt of the cone relative to the branching plane normal vector, Figure : Illustration of the parameters shown in equations 14 and 17. The parameter s shows the tilt of the double cone's principle axis, and g and h are the norms of the energy difference gradient and derivative coupling vector, respectively, and describes the asymmetry or ellipticity of the cone in the first order picture.