Review of point defect structures in hexagonal close packed metals and across the Periodic Table

TL;DR

This paper provides a comprehensive ab initio dataset of point defect properties in hcp metals, revealing that defect characteristics are mainly influenced by electronic structure rather than lattice geometry.

Contribution

It introduces a large dataset of defect formation energies and elastic properties in hcp metals, highlighting the dominant role of electronic structure over lattice parameters.

Findings

Defect properties are weakly correlated with c/a ratio.

Element position in the Periodic Table primarily determines defect properties.

Vacancy and interstitial relaxation volumes correlate with atomic volumes.

Abstract

We present a comprehensive ab initio dataset of formation energies and elastic properties of intrinsic point defects across all the transition and rare earth hexagonal close packed (hcp) metals, as well as metalloid elements with hcp crystal structure. Point defect properties appear weakly correlated with the c/a ratio of the hcp lattice. Instead, it is the position of an element in the Periodic Table that primarily defines the relaxation volume tensor, elastic dipole tensor and formation energy of a point defect. This suggests that the local variations in the electronic structure and interatomic bonding at the core of a defect dominate its properties, as opposed to long-range elastic deformations. Across all the metals, we find that the relaxation volumes of vacancies and self-interstitial defects are correlated with atomic volumes, with values of -0.35 and 1.46 atomic volumes for a vacancy and a self-interstitial defect, respectively, providing a universally good approximation independent of the crystal structure. This study complements and completes the existing point defect databases spanning body-centred cubic and face-centred cubic metals.