A first-principles study on structural stability and mechanical properties of polar intermetallic phases CaZn₂ and SrZn₂

Abstract

Structural stability and electronic properties of polar intermetallic CaZn₂ and SrZn₂ in both CeCu₂-type and MgZn₂-type structures have been investigated using first-principles method. The calculated equilibrium lattice parameters agree closely with the available experimental and other theoretical results. In terms of formation enthalpy, it is discovered that the present compounds with CeCu₂-type structure are energetically more stable than that with MgZn₂-type. They are all mechanically stable according to the criteria of elastic stability. In particular, we have investigated the pressure effect on the compressive behaviour and structural stability of each compound. Subsequently, the bulk modulus, shear modulus, Young’s modulus, theoretical hardness, Poisson’s ratio and Debye temperature in the ground state can be estimated using Voigt–Reuss–Hill homogenization method. Mechanical anisotropy is characterized by the anisotropic factors and direction-dependent Young’s modulus. Finally, the electronic structures are determined to reveal the bonding characteristics of considered phases.

Keywords:

• intermetallic phase
• Laves phase
• mechanical properties
• electronic structure
• first-principles calculations

Acknowledgements

Authors acknowledge the financial support of the National Natural Science Foundation of China [grant number 51464034], [grant number 51301107], [grant number 51264032] and [grant number 51171113], the Innovation Fund Designated for Graduate Students of Jiangxi Province [grant number YC2013-S027], the Hong Kong Scholars Programme [grant number XJ2012025], the Jiangxi Post-doctoral Science Foundation [grant number 2014KY11] and the China Postdoctoral Science Foundation funded project [grant number 2012T50594], [grant number 2014M551866].