Structural, mechanical, electronic and bonding properties of TMB₂ (TM = Y, Sc, Ti) under pressure: a DFT investigation

ABSTRACT

Based on the first-principles calculations, we have systematically investigated the structural stability, mechanical, electronic and bonding properties of TMB₂ (TM = Y, Sc, Ti) under pressure for the first time. The results show that these TMB₂ (TM = Y, Sc, Ti) compounds are structurally and mechanically stable from 0 to 100 GPa. The order of hardness from high to low is TiB₂> ScB₂> YB₂. Both TiB₂ and ScB₂ belong to the type of superhard materials at 0 GPa, but YB₂ is not. These materials soften with pressure increasing, especially for ScB₂, which changed from superhard to hard material at about 80 GPa. The Pugh and Poisson ratio indicated that they all have a brittle behaviour under pressure, and YB₂ is more prone to ductility than ScB₂ and TiB₂. The bond calculation indicates that all bond lengths decrease monotonously under pressure, and the TM–B bond is more sensitive to pressure. The relationship of bond lengths for TM–B and B–B are YB₂> ScB₂> TiB₂ at the same pressure, which suggests that the shorter bonds may lead to a stronger interaction between atoms. Finally, the effects of pressure on the electronic properties are also investigated in detail.

KEYWORDS:

• First-principles
• structural properties
• mechanical properties
• electronic properties
• high pressure

PACS NUMBERS:

• 63.20.dk
• 81.40.Vw
• 62.20.De
• 71.15.Dx
• 91.60.Gf

Disclosure statement

No potential conflict of interest was reported by the author(s).