Electronegativity and electron currents in molecular tunnel junctions

Electronegativity is shown to control charge transfer, energy level alignments, and electron currents in single molecule tunnel junctions, all of which are described through the density matrix. Currents calculated from the one-electron reduced density matrix correct to second order in electron-electron correlation are identical to currents obtained from the one-electron Green's function corrected to second order in electron self-energy. A tight binding model of hexa-1,3,5-triene-1,6-dithiol bonded between metal electrodes is introduced, and the effect of analytically varying electron-electron correlation on electron currents and electronegativity is examined. The model analysis is compared to electronic structure descriptions of a gold-hexatriene (approximated by different exchange-correlation functionals) and Hartree-Fock states as zeroth-order approximations to the one-electron Green's function. Comparison between the model calculations and the electronic structure treatment allows us to relate the ability to describe electronegativity within a single particle approximation to predictions of current-voltage characteristics for molecular tunnel junctions.