A first-principles study on the structural, elastic and electronic properties of the C14 Laves phase compounds TiX₂ (X=Cr, Mn, Fe)

The structural, elastic and electronic properties of nonmagnetic TiCr ₂, TiMn₂ and antiferromagnetic TiFe₂ with hexagonal C14 structure were investigated by mean of the first-principles calculations within the frame work of density functional theory (DFT). The calculated lattice constants were in good agreement with the experimental values. The obtained cohesive energy and formation enthalpy showed TiCr ₂, TiMn₂ and TiFe₂ are of the structural stability from the energetic point of view. The five independent elastic constants were calculated, showing that these compounds are mechanically stable. Then the polycrystalline elastic parameters (bulk modulus B, shear modulus G, Young's modulus E, and Poisson's ratio ν) were obtained by using the Voigt-Reuss-Hill (V-R-H) approximation, and the ductility and plasticity of these compounds were further analyzed. The elastic anisotropy of these compounds was also discussed in details. Finally, the electronic density of states (DOS) and charge density distribution were also calculated, indicating the existence of a combination of metallic, covalent and ionic bonding in these C14 compounds.