Extending the Newns-Anderson model to allow nanotransport studies through molecules with floppy degrees of freedom

TL;DR

This paper extends the Newns-Anderson model to include intramolecular reorganization effects, enabling more accurate studies of electron transport through molecules with floppy degrees of freedom, such as bipyridine.

Contribution

The work introduces an extension of the Newns-Anderson model to account for intramolecular reorganization in molecules with floppy degrees of freedom, supported by electronic structure calculations.

Findings

Intramolecular reorganization can significantly influence molecular transport.

Model parameters for bipyridine differ from outer reorganization due to anharmonicities.

Extended model can be used for transport calculations in experimental molecular junctions.

Abstract

The Newns-Anderson model is ubiquitous in studies of the molecular transport in the presence of solvent (outer) reorganization. The present work demonstrates that intramolecular reorganization can also be significant for the transport through molecules with floppy degrees of freedom, for which the Newns-Anderson model can be extended. The expressions of the model parameters deduced from electronic structure calculations for (4, 4')-bipyridine (44BPY) quantitatively differ from those characteristic for outer reorganization due to strong intramolecular anharmonicities. These expressions can be utilized as input in transport calculations for 44BPY-based molecular junctions of experimental interest [Science 301 (2003) 203, J. Am. Chem. Soc. 130 (2008) 16045, Nano Lett. 12 (2012) 354].