Mechanical properties of B12-based orthorhombic metal carboborides. A first principle study

Structural and mechanical properties of B12-based orthorhombic metal carboborides are studied on the basis of first principle DFT approach. The simulations predict the existence of a new family of phases of the composition MeC2B12 (Me=Mg, Ca, Sr, Sc, Y) with similar structure and space symmetry Imma. It has been found that the predicted phases are thermally (dynamically) stable and have considerably better mechanical properties as compared to the reference compound AlMgB14. The respective calculated isotropic elastic moduli and Vickers hardness are significantly higher (G~ 230-250, E~530-550, and Hv~35-55 GPa). These conclusions were confirmed by direct calculations of shear strength for the above phases, which demonstrated the increase of 30-50% in different directions. The enhanced mechanical characteristics of the MgC2B12 -based phases make them promising for creating novel superhard materials