Unraveling the Anomalous Mechanothermal Properties of Hf ₂ SeB Under High Pressure: A Comprehensive DFT Investigation

The high‐pressure structural, mechanical, electronic, and thermal transport properties of the layered MAB‐phase ternary boride Hf 2 SeB are systematically investigated via first‐principles across a pressure range of 0–50 GPa. Hf 2 SeB crystallizes in a hexagonal P6 3 /mmc structure and retains thermodynamic, mechanical, and dynamical stability throughout the investigated pressure regime. Hydrostatic compression induces pronounced anisotropic lattice contraction, with enhanced stiffness along the basal plane relative to the c‐axis, accompanied by a pressure‐amplified elastic anisotropy. Electronic structure analyses reveal robust metallic conductivity dominated by Hf‐d states near the Fermi level, with a substantial pressure‐induced increase in the electronic density of states. Notably, compression markedly strengthens the mechanical response, with the theoretical Vickers hardness increasing from 12.02 GPa at ambient conditions to 17.52 GPa at high pressure. In parallel, Hf 2 SeB exhibits an ultralow minimum thermal conductivity (0.68–0.90 W m −1 K −1 ) and a continuously rising melting temperature, suggesting its potential for applications in high‐pressure, high‐temperature, and thermomechanically demanding environments, though its oxidation resistance at elevated temperatures remains a critical consideration for practical use.