Work

Characterization of an Unexpected μ3 Adsorption of Molecular Oxygen on Ag(100) with Low-Temperature STM

Year: 2024

Type: article

Abstract: High Resolution Image Download MS PowerPoint Slide Precise description of the interaction between molecular oxygen and metal surfaces is one of the most challenging topics in quantum chemistry. In this work, we use low-temperature scanning tunneling microscopy (STM) to identify and characterize an adsorption state of molecular oxygen that coordinates to three Ag atoms (μ 3 ) on Ag(100). Surprisingly, μ 3 -O 2 cannot be identified as a stable configuration with generalized gradient approximation (GGA)-level density functional theory (DFT) calculations. Through inelastic electron tunneling spectroscopy (IETS), we identify three vibrational modes of individual μ 3 -O 2 and assign them to out-of-plane hindered rotation (HR) at 38.0 meV, in-plane HR at 32.4 meV, and in-plane hindered translation (HT) at 22.0 meV. We determine the barrier for rotational isomerization of μ 3 -O 2 to be 69.3 meV from tunneling electrons-induced rotations. The inability of theory to predict the experiment stems most likely from self-interaction errors inherent to GGA-DFT, which leads to an inaccurate description of localized charges. We speculate that the μ 3 -O 2 configuration represents a formal molecular oxygen anion and assign the ±11 meV excitation in the IETS to a transition between spin–orbit states of the surface-bound anion.

Source: The Journal of Physical Chemistry C

DOI: 10.1021/acs.jpcc.4c06572