Wen-Cheng Hu

Predictions of the structural, electronic and thermodynamic properties of the anti-fluorite-type Mg2Sn under pressure from first principles

Using first-principles calculations based on density functional theory, the structural, electronic and thermodynamic properties of Mg2Sn in anti-fluorite structure under hydrostatic pressure are investigated. Our results for the equilibrium structural parameters are consistent with the previous experimental and theoretical data. The dependences of elastic constants, polycrystalline elastic moduli, Poissons ratio and the anisotropy factor on pressure have been investigated. It is found that pressure has a significant effect on elastic properties due to variations in interatomic distances. In addition, the variations in density of states with applied pressure are determined to reveal the bonding characteristics. Finally, the dependences of bulk modulus and thermodynamic properties of Mg2Sn on pressure and temperature are investigated with the quasi-harmonic Debye model, and the results of thermodynamic properties are consistent with the experimental report.

Predictions of mechanical and thermodynamic properties of Mg17Al12 and Mg2Sn from first-principles calculations

Using first-principles calculations, we predict mechanical and thermodynamic properties of both Mg17Al12 and Mg2Sn precipitates in Mg–Al–Sn alloys. The elastic properties including the polycrystalline bulk modulus, shear modulus, Young’s modulus, Lame’s coefficients and Poisson’s ratio of both Mg17Al12 and Mg2Sn phases are determined with the Voigt–Reuss–Hill approximation. Our results of equilibrium lattice constants agree closely with previous experimental and other theoretical results. The ductility and brittleness of the two phases are characterized with the estimation from Cauchy pressure and the value of B/G. Mechanical anisotropy is characterized by the anisotropic factors and direction-dependent Young’s modulus. The higher Debye temperature of Mg17Al12 phase means that it has a higher thermal conductivity and strength of chemical bonding relative to Mg2Sn. The anisotropic sound velocities also indicate the elastic anisotropies of both phase structures. Additionally, density of states and Mulliken population analysis are performed to reveal the bonding nature of both phases. The calculations associated with phonon properties indicate the dynamical stability of both phase structures. The temperature dependences of thermodynamic properties of the two phases are predicted via the quasi-harmonic approximation.

Structural properties, phase stability, elastic properties and electronic structures of Cu–Ti intermetallics

The structural properties, phase stabilities, anisotropic elastic properties and electronic structures of Cu–Ti intermetallics have been systematically investigated using first principles based on the density functional theory. The calculated equilibrium structural parameters agree well with available experimental data. The ground-state convex hull of formation enthalpies as a function of Cu content is slightly symmetrical at CuTi with a minimal formation enthalpy (–13.861 kJ/mol of atoms), which indicates that CuTi is the most stable phase. The mechanical properties, including elastic constants, polycrystalline moduli and anisotropic indexes, were evaluated. G/B is more pertinent to hardness than to the shear modulus G due to the high power indexes of 1.137 for G/B. The mechanical anisotropy was also characterized by describing the three-dimensional (3D) surface constructions. The order of elastic anisotropy is Cu4Ti3 > Cu3Ti2 > α-Cu4Ti > Cu2Ti > CuTi > β-Cu4Ti > CuTi2. Finally, the electronic structures were discussed and Cu2Ti is a semiconductor.

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

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.