The Jahn-Teller Effects in Chemical Reactions and Materials Science

Abstract

In a semi-review paper (a review with novel results included), we note first that the so-called Jahn-Teller effects (JTEs), in their presently recognized four modifications, emerge as particular cases of a more general law, stating that “Nature tends to avoid degeneracies and pseudo-degeneracies in atomic matter by means of spontaneous symmetry breaking (SSB)”. This “Law of Nature” obviously influences all the relevant properties of polyatomic systems, including those with direct applications in materials science and engineering, as well as in materials transformations, notably, in chemical reactions. The exploration to the latter is quite novel: we show that the energy barriers in chemical transformations are controlled by the pseudo-JTE (PJTE), opening uncharted ways of catalytic action. The applications of JTEs theory in materials science is already more advanced, utilizing the SSB-induced special nuclear dynamics, which is very sensitive to external perturbations. One of its novel aspects is to modify the properties of the system by means of external influence targeting its JTEs parameters, their underlying degeneracies. We show here some notable trends with illustrative examples, including the JTEs in local centers in crystals used as qubits in quantum information storage, alteration of whole crystal lattice properties by inducing the JTE in one of its sublattices, planarization of puckered (buckled) two-dimensional systems by coordination to atoms that quench their PJTE-induced out-of-plane distortion, and the origin of a whole series of solid state properties of perovskite crystals, triggered by the local PJTE.