Title: Modelling non-adiabatic processes using correlated electron-ion dynamics
Author(s): 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.
European Physical Journal B , 77, No. 3, pp. 305-329 (October 2010)
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.
Title: Nonconservative generalized current-induced forces
Author(s): Todorov T.N., Dundas D., McEniry E.J.
Physical Review B, 81, No. 7, Art. No. 075416 (2010)
A recent result for the curl of forces on ions under steady-state current in atomic wires with noninteracting electrons is extended to generalized forces on classical degrees of freedom in the presence of mean-field electron-electron screening. Current is described within a generic multiterminal picture, forces within the Ehrenfest approximation, and screening within an adiabatic, but not necessarily spatially local, mean-field picture.
Title: Density-potential mapping in time-dependent density-functional theory
Author(s): Maitra N.T., Todorov T.N., Woodward C., Burke K.,
Physical Review A, 81, No. 4 (2010)
The key questions of uniqueness and existence in time-dependent density-functional theory are usually formulated only for potentials and densities that are analytic in time. Simple examples, standard in quantum mechanics, lead, however, to nonanalyticities. We reformulate these questions in terms of a nonlinear Schrodinger equation with a potential that depends nonlocally on the wave function.