Defect processes in Be$_{12}$X Beryllides

TL;DR

This study uses density functional theory to analyze defect stability in Be12X intermetallics, revealing dominant defect processes and their implications for fusion energy materials.

Contribution

It provides the first detailed computational analysis of defect processes in Be12X intermetallics, highlighting their defect energetics and stability.

Findings

Schottky disorder is the lowest energy defect process.

Be Frenkel disorder is comparable in Be12V and Be12Ti.

Clustering of certain defects is energetically favorable.

Abstract

The stability of intrinsic point defects in Be$_{12}$X intermetallics (where X = Ti, V, Mo or W) are predicted using density functional theory simulations and discussed with respect to fusion energy applications. Schottky disorder is found to be the lowest energy complete disorder process, closely matched by Be Frenkel disorder in the cases of Be$_{12}$V and Be$_{12}$Ti. Antitisite and X Frenkel disorder are of significantly higher energy. Small clusters of point defects including Be divacancies, Be di-interstitials and accommodation of the X species on two Be sites were considered. Some di-interstitial, divacancy and X$_{2Be}$ combinations exhibit negative binding enthalpy (i.e. clustering is favourable), although this is orientationally dependent. None of the Be$_{12}$X intermetallics are predicted to exhibit significant non-stoichiometry, ruling out non-stoichiometry as a mechanism for accommodating Be depletion due to neutron transmutation.