Renner-Teller/Jahn-Teller intersections along the collinear axes of polyatomic molecules: C2H2+ as a case study
Journal of Chemical Physics
Recently we discussed the Renner-Teller effect in triatomic molecules ͓J. Chem. Phys. 125, 094102 ͑2006͔͒. In that article the main message is that the Renner-Teller phenomenon, just like the Jahn-Teller phenomenon, is a topological effect. Now we extend this study to a tetra-atomic system, namely, the C 2 H 2 + ion, for which topological effects are revealed when one atom surrounds the triatom axis or when two atoms surround ͑at a time͒ the two-atom axis. The present study not only supports
... ot only supports the findings of the previous study, in particular, the crucial role played by the topological D matrix for diabatization, but it also reveals new features which are expected to be more and more pronounced the larger the original collinear molecule. As already implied, shifting away two atoms from the collinear molecular axis does not necessarily abolish the ability of the remaining two atoms to form topological effects. Moreover, the study indicates that when the two hydrogens are shifted away, the CC axis produces two kinds of topological effects: ͑1͒ a Renner-Teller effect ͑characterized by a topological phase of 2͒ which is revealed when the two hydrogens surround, rigidly, this axis ͑as mentioned above͒, and ͑2͒ a Jahn-Teller effect ͑characterized by a topological phase of ͒ which is revealed when one of the hydrogens surrounds this axis while the other hydrogen is clamped to its position.