First-principles calculation on the transport properties of molecular wires between Au clusters under equilibrium

TL;DR

This study uses first-principles calculations combining Green's function and density functional theory to analyze the conductance of various gold-molecule-gold junctions, aligning theoretical results with experimental data.

Contribution

It introduces a method to accurately determine the Fermi level position using UPS data, improving the agreement between theoretical and experimental conductance calculations.

Findings

Calculated conductances qualitatively match experimental values.

Fermi level alignment is crucial for accurate conductance predictions.

The approach accounts for experimental uncertainties in UPS measurements.

Abstract

Based on the matrix Green's function method combined with hybrid tight-binding / density functional theory, we calculate the conductances of a series of gold-dithiol molecule-gold junctions including benzenedithiol (BDT), benzenedimethanethiol (BDMT), hexanedithiol (HDT), octanedithiol (ODT) and decanedithiol (DDT). An atomically-contacted extended molecule model is used in our calculation. As an important procedure, we determine the position of the Fermi level by the energy reference according to the results from ultraviolet photoelectron spectroscopy (UPS) experiments. After considering the experimental uncertainty in UPS measurement, the calculated results of molecular conductances near the Fermi level qualitatively agree with the experimental values measured by Tao et. al. [{\it Science} 301, 1221 (2003); {\it J. Am. Chem. Soc.} 125, 16164 (2003); {\it Nano. Lett.} 4, 267 (2004).]