Defect formation and migration in MAlB (M=Mo, W) and N2AlB2 (N=Cr, Fe) : A first-principles study

Abstract

The exceptional properties of MAB phases (where M = transition metal, A = aluminum, and B = boron) make them a promising option for various applications. However, their usage in most fields requires an understanding of the defect formation and migration processes, which can aid in designing durable and functional materials. Through density functional theory calculations, we investigated the stability and mobility of the most prominent point and extended defects in MAlB (where M = Mo and W) and ${\mathrm{N}}_{2}{\mathrm{AlB}}_{2}$ (where N = Cr and Fe) MAB phases under different chemical conditions. Our findings indicate that ${\mathrm{V}}_{\mathrm{B}}/{\mathrm{N}}_{\mathrm{Al}}$ is the easiest defect to form under M/N-rich conditions. We observed that vacancy and antisite defects form more easily than interstitial ones in all studied systems. We also investigated different extended structural defects and stacking faults and revealed the stability of relevant compositional defects and tilt/rotational boundaries in MAlB and ${\mathrm{N}}_{2}{\mathrm{AlB}}_{2}$. Our results suggest that these systems can likely be synthesized by tuning the experimental conditions. We additionally observed grain boundary formation in ${\mathrm{N}}_{2}{\mathrm{AlB}}_{2}$ and compared our findings with relevant experiments.