Correlated electron–ion dynamics: the excitation of atomic motion by energeticelectrons

Abstract

Correlated electron–ion dynamics (CEID) is an extension of molecular dynamicsthat allows us to introduce in a correct manner the exchange of energy betweenelectrons and ions. The formalism is based on a systematic approximation: smallamplitude moment expansion. This formalism is extended here to include theexplicit quantum spread of the ions and a generalization of the Hartree–Fockapproximation for incoherent sums of Slater determinants. We demonstrate thatthe resultant dynamical equations reproduce analytically the selection rules forinelastic electron–phonon scattering from perturbation theory, which control themutually driven excitations of the two interacting subsystems. We then use CEIDto make direct numerical simulations of inelastic current–voltage spectroscopyin atomic wires, and to exhibit the crossover from ionic cooling to heating as afunction of the relative degree of excitation of the electronic and ionic subsystems.