Structural, Mechanical, and Electronic Properties of the Compounds Sc2B and ScB under Pressure

Abstract

In conjunction with particle swarm optimisation techniques, we have delved into the crystal structure of low boron Sc–B compounds within 100 GPa. The trigonal Sc₂B with space group P-3m1 is consistently stable over a pressure range of 0–100 GPa. Moreover, this P-3m1-Sc₂B structure is mechanically and dynamically stable, as evidenced by elastic constant and phonon dispersion curve calculations. The hexagonal ScB with space group P-6m2 is always stable in the pressure region 0–92.6 GPa. Structurally, the B atoms of the structure form a separate layer that is stacked alternately with the Sc layer along the c direction, and at high pressures it changes phase to an orthorhombic Fmmm structure. Interestingly, calculations of elastic constants and hardness show that both phases of Sc₂B and ScB have high hardness values at ambient pressure, especially P-6m2-ScB, which unexpectedly reaches a hardness value of 26.8 GPa, an incompressible material.