STRUCTURAL, ELASTIC AND MECHANICAL PROPERTIES OF ( = , , ): A DFT STUDY.

Mechanical properties and the effect of metallic bonding on the hardness of transition-metal nitrides (, and ) compounds are studied using the first-principles calculation. Present results show that these transition-metal nitrides are mechanically stable and the and are ductile, whereas is predicted to be brittle. Moreover, it is found that the high hardness of , and exhibits a remarkable decrease with transition-metal changed from to , and the metallic d-d interactions play important roles on determining the hardness of transition-metal nitrides. [ABSTRACT FROM AUTHOR]