First principle DFT simulations are employed to study structural and mechanical properties of AlMgB14 and related orthorhombic B12-based metal borides and carbo-borides. The simulations predict the existence of a new family of AlMgB14 -related phases (MeC2B12; Me= Mg, Ca, Sr, Sc, Y) with the structure similar to that of experimentally observed earlier compound MgC2B12, which have significantly enhanced mechanical characteristics. The calculated shear and Young’s moduli of these phases are nearly 250 and 550 GPa, respectively, and estimated Vickers hardness is 40-55 Gpa. Direct simulations of shear strength indicate the 50% increase in all directions as compared to the basic reference AlMgB14 compound, which suggests their potential as superhard materials.

In order to study the mechanical behavior of multicomponent polycrystalline composites, a microelsticity model was developed based on direct minimization of free energy of a system by means of Monte Carlo algorithms. The model was employed to examine the effect of enhancement of mechanical properties of composites in relation to parent components. The results of simulations suggest that the classical Duhamel-Neumann theory only fails to explain this effect, and in order to reproduce it, the interfacial inter-grain energy has to be taken into account.