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Beyond Ehrenfest: correlated non-adiabatic molecular dynamics

Horsfield, AP; Bowler, DR; Fisher, AJ; Todorov, TN; Sanchez, CG; (2004) Beyond Ehrenfest: correlated non-adiabatic molecular dynamics. J PHYS-CONDENS MAT , 16 (46) 8251 - 8266. 10.1088/0953-8984/16/46/012.

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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.

Type:Article
Title:Beyond Ehrenfest: correlated non-adiabatic molecular dynamics
DOI:10.1088/0953-8984/16/46/012
Keywords:QUANTIZED HAMILTON DYNAMICS, NANOSCALE CONDUCTORS, POWER DISSIPATION, QUANTUM-MECHANICS, TIGHT-BINDING, ATOMIC WIRES, SIMULATION, WAVEPACKETS
UCL classification:UCL > School of BEAMS > Faculty of Maths and Physical Sciences > London Centre for Nanotechnology
UCL > School of BEAMS > Faculty of Maths and Physical Sciences > Physics and Astronomy

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