We present a first-principles analysis of the wurtzite pseudo-ternary (Al,Sc,B)N to elucidate the structural origin of a decoupling between stiffness C33 and piezoelectric response e33 upon boron incorporation, using DFT-relaxed 100-atom special quasirandom structures across a broad composition range. Pair distribution function analysis reveals interstitial threefold-coordinated boron atoms that have displaced from the tetrahedral cation site. Direct structural analysis establishes their preferential orientation along the c-axis and identifies a scandium-activated creation mechanism. The vertical coordination asymmetry of each cation is quantified through a site-specific axial asymmetry ratio (AAR), showing that boron incorporation progressively symmetrizes the Sc environment. Correlation with Born effective charges demonstrates that this symmetrization is the mechanism behind the piezoelectric enhancement.
@article{arxiv.2605.15568,
title = {Local distortions as a source of piezoelectric/stiffness decoupling in B-doped AlScN},
author = {Laszlo Wolf and Geoff L. Brennecka and Vladan Stevanović},
journal= {arXiv preprint arXiv:2605.15568},
year = {2026}
}