Computational Investigation into Synthesis of Transition Metal Borides

Borides of transition metals and high-entropy alloys offer novel opportunities to design materials that demonstrate phase stability, high strength, and thermal oxidation resistance at high temperatures and under extreme conditions. Identifying mechanically strong and chemically inert transition metal borides requires an understanding of the synthesizability of different transition metal borides, as well as their mechanism of growth during boriding of such metals. We performed <i>ab initio</i> Density Functional Theory simulations to quantify phase stability, formation energies of point and extended defects, and point defect migration barriers in crystalline borides of transition metals and their alloys. A point defect model based on the computed defect concentrations and ionic mobilities was used to explain the experimentally observed thicknesses of boride films formed by the boriding of different transition metals and alloys. Thermodynamic (formation energies and stability) and kinetic (energy barriers and mobilities) data from these ab initio simulations were also used to create a graph neural network model for the screening of compositional phase space of high-entropy borides to identify promising candidates with high phase stability and synthesizability.