Unexpected Ground-State Structure and Mechanical Properties of Ir(2)Zr Intermetallic Compound

Using an unbiased structure searching method, a new orthorhombic Cmmm structure consisting of ZrIr(12) polyhedron building blocks is predicted to be the thermodynamic ground-state of stoichiometric intermetallic Ir(2)Zr in Ir-Zr systems. The formation enthalpy of the Cmmm structure is considerably lower than that of the previously synthesized Cu(2)Mg-type phase, by ~107 meV/atom, as demonstrated by the calculation of formation enthalpy. Meanwhile, the phonon dispersion calculations further confirmed the dynamical stability of Cmmm phase under ambient conditions. The mechanical properties, including elastic stability, rigidity, and incompressibility, as well as the elastic anisotropy of Cmmm-Ir(2)Zr intermetallic, have thus been fully determined. It is found that the predicted Cmmm phase exhibits nearly elastic isotropic and great resistance to shear deformations within the (100) crystal plane. Evidence of atomic bonding related to the structural stability for Ir(2)Zr were manifested by calculations of the electronic structures.