Elastic constants and tensile properties of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mi>Al</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:mi>OC</mml:mi></mml:mrow></mml:math>by density functional calculations

${\mathrm{Al}}_{2}\mathrm{OC}$ is a compound that forms as a nanoscale grain-boundary crystalline film in silicon carbide ceramics, and is responsible for imparting high low-temperature toughness and high-temperature creep strength in these materials. The elastic properties and ultimate strengths properties of ${\mathrm{Al}}_{2}\mathrm{OC}$ are determined from first-principles calculations. The crystal structure of ${\mathrm{Al}}_{2}\mathrm{OC}$ was approximated by an optimized model based on the wurtzite structure. The full set of single-crystal elastic stiffness ${c}_{ij}$ was calculated, from which the polycrystalline elastic constants were obtained by using the Voigt-Reuss-Hill averaging scheme. The tensile properties and the ideal strength in $[001]$ direction of ${\mathrm{Al}}_{2}\mathrm{OC}$ were also computed and compared to those of $\mathrm{SiC}$, where it was found that indeed, ${\mathrm{Al}}_{2}\mathrm{OC}$ is the weaker and more brittle phase, supporting fracture mechanics expectations for $\mathrm{SiC}$ containing ${\mathrm{Al}}_{2}\mathrm{OC}$-type intergranular films.