Beyond Ehrenfest: correlated non-adiabatic molecular dynamics

A.P. Horsfield, D.R. Bowler, A.J. Fisher, Tchavdar Todorov, C.G. Sanchez

Research output: Contribution to journalArticlepeer-review

80 Citations (Scopus)

Abstract

A method for introducing correlations between electrons and ions that is computationally affordable is described. The central assumption is that the ionic wavefunctions are narrow, which makes possible a moment expansion for the full density matrix. To make the problem tractable we reduce the remaining many-electron problem to a single-electron problem by performing a trace over all electronic degrees of freedom except one. This introduces both one- and two-electron quantities into the equations of motion. Quantities depending on more than one electron are removed by making a Hartree-Fock approximation. Using the first-moment approximation, we perform a number of tight binding simulations of the effect of an electric current on a mobile atom. The classical contribution to the ionic kinetic energy exhibits cooling and is independent of the bias. The quantum contribution exhibits strong heating, with the heating rate proportional to the bias. However, increased scattering of electrons with increasing ionic kinetic energy is not observed. This effect requires the introduction of the second moment.
Original languageEnglish
Pages (from-to)8251-8266
Number of pages16
JournalJournal of Physics: Condensed Matter
Volume16
Issue number46
DOIs
Publication statusPublished - 24 Nov 2004

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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