Structural diversity and electronic properties of neodymium borides under high pressure

Rare earth (RE) borides have garnered significant attention due to their high mechanical strength, superconductivity, and novel electronic properties. In this study, we systematically investigate the structural, electronic, and mechanical properties of RE neodymium borides across a wide range of pressures. Various stoichiometries of Nd-B compounds are predicted using the unbiased CALYPSO structure search method and density functional theory calculations. Our findings indicate that the newly predicted NdB₅, NdB₇, and NdB₈compounds are thermodynamically and mechanically stable at high pressures. Detailed analyses of the electronic band structure and density of states reveal that all neodymium borides exhibit metallic behaviour. The hardness of the stable phases has been evaluated using an empirical model. Notably, NdB₅compound could also be dynamically and mechanically stable at ambient pressure with an estimated hardness of approximately 24.82 GPa, suggesting that NdB₅is a potential hard metal boride. Our results provide valuable insights into the structural, electronic, and mechanical properties of Nd-B compounds, enhancing our understanding of their potential applications in various fields.