Computational Investigation of Thermodynamic Stability in Novel High Entropy MAB Phases Based on the Cr₄AlB₄ Structure

High Entropy Alloys (HEAs) represent a new materials design approach with unique properties stemming from Configurational Entropy (CE) that stabilizes solid solution phases. We explore applying the HEA concept to MAB phase materials, which combine metallic and ceramic properties. Our target is Cr₄AlB₄, a MAB phase exhibiting excellent mechanical strength, thermal stability, and electrical conductivity. We substituted Cr atoms with transition metals to examine thermodynamic stability of multi element MAB phases using first principles Density Functional Theory (DFT) calculations. By computing 0 K energy above hull (ΔH_hull), we assessed stability of multi element systems containing Cr, Ti, W, Mn, Mo, and Fe by comparing each composition's DFT calculated formation energy with the convex hull of all known competing phases. Our findings show certain elemental combinations yield thermodynamically stable or nearly stable phases. Notably, stable ground states are predicted for elements like Cr₃WAlB₄ (ΔH_hull = +0.003 eV/atom) and Cr₃MnAlB₄ (ΔH_hull = -0.0001 eV/atom). We also examined CE effects on phase stability at high temperatures, proving that several metastable compositions, including Cr_1.33Mo_1.33W_1.33AlB₄, become thermodynamically stable at experimentally relevant synthesis temperatures through Gibbs Energy Above Hull calculations. These results provide vital theoretical guidance for targeted synthesis of a novel family of stable HE-MAB phases for extreme environment applications.