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Abstract: We present a study of the energetics, elastic properties and electronic structures of the Laves C 15-Mg2RE (RE=La, Ce, Pr, Nd, Pm, Sm, and Gd) through density functional theory (DFT). The calculated lattice constants are in good agreement with available experimental data and previously theoretical predictions. The formation enthalpies, elastic constants, bulk moduli, and pressure derivatives of the C 15-type Mg2RE are predicted. Young’s moduli, shear moduli, and anisotropic ratios of the C 15-type Mg2RE are further estimated from the calculated single-crystal elastic constants. The present results indicate that the Young’s modulus and anisotropic ratio of C 15-Mg2RE are all less than those of B 2-MgRE and D03-Mg3RE. The electronic densities of states and bonding charge densities have been discussed in details. The characteristic of mechanical properties has been explained from the point view of electronic structure. The present calculation indicates that C 15-Mg2RE might be more ductile than B 2-MgRE and D03-Mg3RE. [Copyright &y& Elsevier]

Abstract: Ab initio calculations for the total energy and elastic properties of the C15-type Al2RE (RE=Sc, Y, Lanthanide) at T =0K have been performed by using the projector augmented-wave (PAW) method within the generalized gradient approximation (GGA). The lattice constants, formation enthalpies, elastic constants, bulk modulus and its pressure derivatives of the C15-type Al2RE are obtained. Poisson’s ratios, Young’s modulus, shear modulus and the ratios of elastic anisotropy are also estimated in the present work. By using the Debye–Grüneisen model, the Debye temperatures, Grüneisen constants and the coefficients of thermal expansion at T =300K are obtained for the C15-type Al2RE. The present calculated results are in good agreement with reported experimental values and with other theoretical calculations available as well. [Copyright &y& Elsevier]

Abstract: The electronic structure, the total energy and elastic properties of the Mn3AlN with anti-peroviskite structure have been calculated at T =0K by using the projector augmented-wave (PAW) method within LDA and GGA. The lattice constants, elastic constants, bulk modulus and its pressure derivatives of Mn3AlN are obtained. The Gibbs energies of different magnetic states are estimated by using quasi-harmonic Debye–Grüneisen model. The changes of volume resulted from the magnetic transformation are discussed according to the present calculations. The transformation from ferromagnetic to paramagnetic phase for Mn3AlN happens at 250K. [Copyright &y& Elsevier]

The thermophysical and electronic properties as well as the lattice dynamics of ThCr 2 Si 2 -type CaX 2 Si 2 (X = Ni, Zn, Cu, Ag, Au) are investigated by using first-principles calculations based on the density functional theory (DFT). The lattice constants and formation enthalpies of CaX 2 Si 2 are elaborately calculated. All of calculated results are in good agreement with the experimental data. The mechanical properties, including single crystal elastic constants, polycrystalline elastic moduli and orientation dependence of Young’s moduli and shear moduli of CaX 2 Si 2 , and electronic properties such as the electronic density of states (DOS) and charge density distribution of CaX 2 Si 2 are predicted in this work. The calculated charge density indicates the presence of covalent bonding between Si–Si atoms in CaX 2 Si 2 compounds. The calculations of phonon spectrum and phonon density of states for CaX 2 Si 2 are also completed. The imaginary frequency of CaZn 2 Si 2 in the vicinity of Γ point indicates that the CaZn 2 Si 2 phase is dynamically instable at the ground state. Based on the phonon spectrum calculation, the predictions of heat capacity and entropy for CaX 2 Si 2 are accomplished with quasi-harmonic approximation. [ABSTRACT FROM AUTHOR]

Abstract: The phase stability, electronic, elastic and thermodynamic properties of V5Si3 has been investigated by using first-principles calculations based on the density functional theory (DFT). In the present calculations, three phases of V5Si3 (Cr5B3-prototype, W5Si3-prototype and Mn5Si3-prototype) have been taken into account to check the phase stability. The calculated formation enthalpies indicate that the W5Si3-prototype is the stable phase which is in agreement with experiments, whereas the Cr5B3-prototype is a potential metastable phase. The elastic constants, bulk modulus, shear modulus and Young’s modulus are calculated in the present work, and are very close to that of the Nb5Si3. The density of states and bonding charge density of V5Si3 within the W5Si3-phase are obtained indicating a strong covalent character of the bonds. Finally, using the Debye-model, the Debye temperature, heat capacity, and thermal expansion have also been calculated and are in good agreement with experimental results. [Copyright &y& Elsevier]