Copper-doped beryllium and beryllium oxide interface: A first-principles study

Abstract

Beryllium oxide (BeO) serves as a copper (Cu) diffusion barrier in designing Be ablators for inertial confinement fusion. We study the preferential site substitution of beryllium (Be) by Cu at the Be/BeO interface via large-scale density functional calculations. We first systematically study structures and properties of bulk and surface structures of Cu, Be and BeO, and two interface models are constructed with three concentrations of Cu dopants, i.e., 0.89 at.%, 0.45 at.% and 0.22 at.%. We then perform a thorough study on four different substitution sites with analysis on the atomic structures and electronic structures including the partial density of states, the bader charges, and the charge densities. We elucidate the origin of the increased substitution energy for different substitution sites, which is a result as the Cu dopants lose more electrons with the presence of more nearby O atoms and less adjacent Be atoms. The above changes of atomic structures and electronic structures explain the favorable and unfavorable substitutions of Be by Cu in the Be and BeO layers, respectively. This work provides insightful information for utilizing BeO as a valid candidate for stopping Cu diffusion.