DFT study on phase stability of CrB, MoB, and WB in α, β phases, and CrB2, MoB2, and WB2 in hP6 phase

Abstract

Transition metal borides are promising materials commonly used in high-temperature structural applications. This study examines the structural, mechanical, vibrational, and electronic properties of MB (M represents Cr, Mo, or W and B is Boron) in both α and β phases, as well as MB₂ compounds in the hP6 phase. These analyses were conducted using first-principles density functional theory calculations to evaluate their suitability for high-temperature structural applications. It was determined that the CrB, MoB, and WB compounds in α and β phases, as well as CrB₂, MoB₂, and WB₂ in the hP6 phase, exhibit thermodynamic stability due to their negative heat of formation. The elastic constants of all the phases demonstrate mechanical stability. The Vickers hardness results indicate that all compounds are hard, with WB₂ (40.16 GPa) classified as superhard. Phonon dispersion curves confirm the dynamic stability of all compounds. Additionally, all compounds exhibit metallic characteristics due to the overlap between the valence and conduction bands at the Fermi energy level. These materials demonstrate thermodynamic, mechanical, and dynamic stability, making them suitable for high-temperature structural applications such as gas turbine engines and aerospace. In addition, WB₂ can be used in machining industries such as grinding or cutting soft materials.