Scanning tunneling microscopy current from localized basis orbital density functional theory

TL;DR

This paper introduces a novel method combining localized orbital DFT with wave function propagation to accurately compute elastic STM currents, validated by experiments on CO on Cu(111).

Contribution

The method improves the accuracy of STM current calculations from localized orbital DFT by propagating wave functions using the total DFT potential.

Findings

Successfully reproduces experimental STM images of CO on Cu(111)

Allows analysis of tip orbital contributions to tunneling currents

Provides a practical approach for STM simulations from localized basis DFT

Abstract

We present a method capable of calculating elastic scanning tunneling microscopy (STM) currents from localized atomic orbital density functional theory (DFT). To overcome the poor accuracy of the localized orbital description of the wave functions far away from the atoms, we propagate the wave functions, using the total DFT potential. From the propagated wave functions, the Bardeen's perturbative approach provides the tunneling current. To illustrate the method we investigate carbon monoxide adsorbed on a Cu(111) surface and recover the depression/protrusion observed experimentally with normal/CO-functionalized STM tips. The theory furthermore allows us to discuss the significance of $s$- and $p$-wave tips.