Unexpected Ground-State Structure and Mechanical Properties of Ir2Zr Intermetallic Compound

Abstract

Using an unbiased structure searching method, a new orthorhombic Cmmm structure consisting of ZrIr12 polyhedron building blocks is predicted to be the thermodynamic ground-state of stoichiometric intermetallic Ir2Zr in Ir-Zr systems. The formation enthalpy of the Cmmm structure is considerably lower than that of the previously synthesized Cu2Mg-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-Ir2Zr 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 Ir2Zr were manifested by calculations of the electronic structures.