Abstract
As a promising candidate for hard coating, the thermodynamic stability as well as the elastic properties, of ScB 2 -VB 2 mixtures exhibiting the AlB 2 -type structure are examined using a combination of the cluster-expansion method and the first-principles calculations. Our prediction reveals that, upon cooling the mixtures to low temperatures, Sc and V atoms displays a strong preference for being surrounded by atoms of the opposite type, which reside in the second coordination shell of the metal sublattice. Such a configurational preference indicates a feasibility to fabricate Sc 1 − x V x B 2 in the form of superlattices, as described by periodic arrangements of ScB 2 and VB 2 layers of different thickness along the ¡0001¿ direction. Interestingly, the stiffness, shear strength, and hardness of Sc 1 − x V x B 2 , where 0.375 ≲ x ≲ 0.625, in the form either of superlattice structures or of random solid solutions show significant positive deviations from the linear Vegard’s law, which can be understood in terms of the electronic band filling of the bonding states of Sc 1 − x V x B 2 . These findings also reveal that the elastic moduli and hardness of Sc 1 − x V x B 2 are governed by the contents of ScB 2 and VB 2 constituting the mixtures, rather than by the atomic configuration of Sc and V.
Published Version
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