Adiabatic approximation and related issues including topological implications
António J. C. Varandas · Imprensa da Universidade de Coimbra eBooks · 2011
We provide a perspective on several issues of the adiabatic approximation to the fundamental equation of quantum chemistry as suggested by Born and Oppenheimer: separation of the electronic and nuclear motions, coupledchannel treatment, scaling properties, validity, and diabatic states.The need for its generalization such as to account for the topological implications that arise from the separation of the electronic (fast) and nuclear (slow) degrees of freedom is also described in some detail by focusing on Jahn-Teller systems.Although considerable work has been reported on the energetics and dynamics of two-fold degeneracies of the conical type, the list of references on higher electronic degeneracies is meager due to enhanced theoretical difficulty.For high degeneracies, it may therefore be convenient to avoid the dynamics altogether by making use instead of symmetry invariants.This short review will cover both types of approaches to the electron-nuclei coupling problem, but focusing on work carried out at the author's group.