Adsorption and STM imaging of tetracyanoethylene on Ag(001): An ab-initio study

TL;DR

This study uses ab-initio calculations to analyze how tetracyanoethylene adsorbs on Ag(001), revealing preferred configurations, electronic changes, and STM images that match experimental observations.

Contribution

It provides detailed theoretical insights into TCNE adsorption structures, electronic properties, and STM images on Ag(001), employing a novel spatial extrapolation technique.

Findings

On-top adsorption configuration is most favorable.

Electron transfer from substrate to TCNE's LUMO occurs.

Calculated STM images agree well with experimental data.

Abstract

We investigate the adsorption of a single tetracyanoethylene (TCNE) molecule on the silver (001) surface. Adsorption structures, electronic properties, and scanning tunneling microscopy (STM) images are calculated within density-functional theory. Adsorption occurs most favorably in on-top configuration, with the C=C double bond directly above a silver atom and the four N atoms bound to four neighboring Ag atoms. The lowest unoccupied molecular orbital of TCNE becomes occupied due to electron transfer from the substrate. This state dominates the electronic spectrum and the STM image at moderately negative bias. We discuss and employ a spatial extrapolation technique for the calculation of STM and scanning tunneling spectroscopy (STS) images. Our calculated images are in good agreement with experimental data.