The influence of hydrogen on phase stability, mechanical and electronic properties of B2-ZrCu compound from first-principles

The influence of hydrogen doping on phase stability, mechanical and electronic properties of B2-ZrCu compound was systematically investigated by first-principles calculations. As hydrogen concentration increases, Zr-H bonds and Cu-H bonds makes the metallicity of the system decrease and covalency increase as shown by density of states and electron density difference distribution. Higher covalent character decreases formation enthalpy, which corresponds to better stability. Higher bond covalency also improves hardness and brittleness. However, the lattice structural symmetry and crystallographic packing density play a crucial role in affecting ductility, which make Zr8Cu8H2-<110> display a softer and more ductile character than non-doped Zr8Cu8. Otherwise, the hardness and embrittlement will increase monotonically with the increasement of interstitial hydrogen doping concentrations. The combination of covalency, crystalline symmetry and packing density of interstitial hydrogens play a crucial role in mechanical behavior; while the overall bonding character decides the stability.