Second-order description of Conical Intersections in order to better describe the Conical Intersection Seam (CIS).
One of the new features derived from a second-order representation is that the CIS appears to be curved. Evaluation of the curvature of the seam and of its energy make the design of new conical intersection search algorithms possible.
Furthermore, we are now able to perform a frequency analysis, to distinguish saddle points from minima on the CIS. Some of the potential energy constants used in our studies can also be involved in the rationalization of Jahn Teller spectra.
