Ground-state structure of the hydrogen double vacancy on Pd(111)

TL;DR

This study uses density-functional theory and quantum calculations to determine the ground-state structure of hydrogen double vacancies on Pd(111), revealing quantum effects and specific site preferences consistent with experimental images.

Contribution

It provides the first detailed quantum-mechanical analysis of hydrogen vacancies on Pd(111), identifying the ground-state configuration and quantum effects involved.

Findings

H atom in divacancy prefers hcp site over fcc site

Quantum effects significantly influence hydrogen atom localization

Results align with scanning tunneling microscopy images

Abstract

We determine the ground-state structure of a double vacancy in a hydrogen monolayer on the Pd(111) surface. We represent the double vacancy as a triple vacancy containing one additional hydrogen atom. The potential-energy surface for a hydrogen atom moving in the triple vacancy is obtained by density-functional theory, and the wave function of the fully quantum hydrogen atom is obtained by solving the Schr\"odinger equation. We find that an H atom in a divacancy defect experiences significant quantum effects, and that the ground-state wave function is centered at the hcp site rather than the fcc site normally occupied by H atoms on Pd(111). Our results agree well with scanning tunneling microscopy images.