First-principles calculation of H vibrational excitations at a dislocation core of Pd

TL;DR

This study uses first-principles calculations to analyze hydrogen vibrational excitations at dislocation cores in palladium, revealing how local distortions influence vibrational spectra and match experimental observations.

Contribution

It provides the first ab initio analysis of hydrogen vibrational behavior specifically at dislocation cores in palladium, highlighting the impact of local environment distortions.

Findings

Decreased excitation energy consistent with experiments

Predicted distortions to hydrogen wavefunction

Altered vibrational spectra at dislocation sites

Abstract

Palladium is an ideal system for understanding the behavior of hydrogen in metals. In Pd, H is located both in octahedral sites and in dislocation cores, which act as nanoscale H traps and form Cottrell atmospheres. Adjacent to a dislocation core, H experiences the largest possible distortion in alpha-Pd. Ab initio density-functional theory computes the potential energy for a hydrogen in an octahedral site in alpha-Pd and in a trap site at the core of a partial of an edge dislocation. The Pd partial dislocation core changes the environment for H, distorting the H-Pd bonding which changes the local potential, vibrational spectra, and inelastic form factor for an isolated H atom. The decrease in excitation energy is consistent with experiments, and the calculations predict distortions to the H wavefunction.