First-principles Investigation on Structural, Thermodynamic, and Elastic Properties of Suboxide Zr3O Phase

The lattice dynamics and finite-temperature thermodynamic and mechanical properties of three Zr3O polymorphs,including rhombohedral(R3c),rhombohedral(R32),and hexagonal(P6322)phases,were theoretically investigated using the first-principles calculations.The calculated lattice parameters agree well with experimental values.It is confirmed that the three Zr3O phases exhibit both dynamic and thermodynamic stability.The entropy,enthalpy,Gibbs free energy,specific heat capacity,thermal expansion coefficient,and elastic modulus as a function of temperature from 0 to 1500 K were systematically evaluated.It is found that Zr3O(R3c)is the ground state at 0 K followed by Zr3O(R32)and Zr3O(P6322).Structural phase transitions occur from Zr3O(R3c)to Zr3O(R32)at 50 K and then to Zr3O(P6322)at 540 K.Zr3O(R32)displays superior mechanical properties compared to the other two Zr3O phases.