Mechanical Behavior and Vacancy Tolerance of Multicomponent Tetraboride (CrFeMn)B ₄ : A First‐Principles Study

ABSTRACT

Chemical disorder provides substantial compositional flexibility for boride design, but its effects on the intrinsic strength and defect tolerance of multicomponent tetraborides remain unclear. Here, a Pnnm‐structured multicomponent tetraboride, (CrFeMn)B ₄ , was investigated using first‐principles calculations. Formation energy, phonon, and elastic stability analyses indicated that the proposed structure was energetically favorable relative to the elemental reference states and was both dynamically and mechanically stable. Representative chemically disordered configurations exhibited similar tensile, shear, and compression–shear responses despite their different atomic arrangements, indicating that deformation behavior was governed primarily by the three‐dimensional boron framework rather than by a specific metal sublattice arrangement. Multicomponent alloying reduced shear anisotropy but did not significantly enhance the ideal strength relative to the constituent binary tetraborides. Among the vacancy species considered, boron vacancies were identified as the most energetically favorable. Whereas such vacancies markedly weakened the binary compounds, (CrFeMn)B ₄ exhibited substantially smaller reductions in strength and even vacancy‐induced strengthening in several local environments. This enhanced vacancy tolerance originates from vacancy‐induced structural accommodation and a delayed onset of bond rupture and lattice instability. These results demonstrate that the principal mechanical benefit of multicomponent alloying in tetraborides lies in improving defect tolerance, rather than enhancing defect‐free ideal strength, thus providing an atomistic basis for designing mechanically robust boron‐rich materials.