Superhard metallic compound <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>TaB</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:math> via crystal orientation resolved strain stiffening
Chang Liu, Xinlei Gu, Kan Zhang, Weitao Zheng, Yanming Ma, Changfeng Chen
Abstract
We predict then produce superhard metallic compound ${\mathrm{TaB}}_{2}$ via exploring crystal orientation resolved stress-strain relations. First-principles calculations identify prominent strain stiffening that generates superhigh indentation strengths of 46--49 GPa in the (001) oriented ${\mathrm{TaB}}_{2}$ crystal; in sharp contrast, dynamic instability diminishes strain stiffening even causes softening, leading to notably lower strengths around 30 GPa in the (110) and (100) orientations. Ensuing experimental synthesis creates well crystallized and textured (001) oriented ${\mathrm{TaB}}_{2}$ that exhibits indentation hardness of 45.9 GPa and electrical resistivity of $1.71\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}\phantom{\rule{4pt}{0ex}}\mathrm{\ensuremath{\Omega}}\phantom{\rule{0.16em}{0ex}}\mathrm{m}$, validating key superhard and metallic benchmarks. The present findings showcase an enabling protocol of crystal configuration engineering for selective property optimization, opening a path for rational design and discovery of long-sought but hitherto scarcely produced superhard metallic materials among vast transition-metal compounds.