Modelling non-adiabatic processes using correlated electron-ion dynamics

• Published in: The European physical journal. B, Condensed matter physics Condensed matter physics, 2010-10, Vol.77 (3), p.305-329
• Main Authors: McEniry, E. J., Wang, Y., Dundas, D., Todorov, T. N., Stella, L., Miranda, R. P., Fisher, A. J., Horsfield, A. P., Race, C. P., Mason, D. R., Foulkes, W. M.C., Sutton, A. P.
• Format: Article
• Language: English
• Subjects: Colloquium; Complex Systems; Condensed Matter Physics; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Electronic transport in condensed matter; Electrons; Exact sciences and technology; Fluid- and Aerodynamics; Nuclear radiation; Physics; Physics and Astronomy; Scattering by phonons, magnons, and other nonlocalized excitations; Solid State Physics; Theory of electronic transport; scattering mechanisms; Toy industry
• ISSN: 1434-6028; 1434-6036
• DOI: 10.1140/epjb/e2010-00280-5

. Here we survey the theory and applications of a family of methods (correlated electron-ion dynamics, or CEID) that can be applied to a diverse range of problems involving the non-adiabatic exchange of energy between electrons and nuclei. The simplest method, which is a paradigm for the others, is Ehrenfest Dynamics. This is applied to radiation damage in metals and the evolution of excited states in conjugated polymers. It is unable to reproduce the correct heating of nuclei by current carrying electrons, so we introduce a moment expansion that allows us to restore the spontaneous emission of phonons. Because of the widespread use of Non-Equilibrium Green's Functions for computing electric currents in nanoscale systems, we present a comparison of this formalism with that of CEID with open boundaries. When there is strong coupling between electrons and nuclei, the moment expansion does not converge. We thus conclude with a reworking of the CEID formalism that converges systematically and in a stable manner.