The Static and Dynamic Lattice Changes Induced by Hydrogen Adsorption on NiAl(110)

TL;DR

This study investigates how atomic hydrogen adsorption affects the static and dynamic properties of NiAl(110) surfaces at 130 K, revealing three distinct hydrogen phases and their structural and vibrational characteristics.

Contribution

It provides detailed experimental insights into the phases and lattice changes of hydrogen on NiAl(110), comparing findings with theoretical models.

Findings

Hydrogen exists in three phases: itinerant, ordered superstructure, and disordered gas.

Ordered superstructure forms between 0.4 ML and 0.6 ML coverage.

Hydrogen exhibits no vibrational modes at low coverage due to quantum tunneling.

Abstract

Static and dynamic changes induced by adsorption of atomic hydrogen on the NiAl(110) lattice at 130 K have been examined as a function of adsorbate coverage. Adsorbed hydrogen exists in three distinct phases. At low coverages the hydrogen is itinerant because of quantum tunneling between sites and exhibits no observable vibrational modes. Between 0.4 ML and 0.6 ML, substrate mediated interactions produce an ordered superstructure with c(2x2) symmetry, and at higher coverages, hydrogen exists as a disordered lattice gas. This picture of how hydrogen interacts with NiAl(110) is developed from our data and compared to current theoretical predictions.