International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

Calculations have been performed to study the structural, electronic, elastic, mechanical, thermodynamical and phonon properties of LuS and LuTe with the generalized gradient approximation for exchange and correlation. The calculated lattice constants, bulk modulus, its pressure derivative and elastic constants are calculated. The calculated values of lattice constant are in good agreement with the experimental and theoretical results. The elastic constants have been derived from the slopes of the acouistic branches in the phonon dispersion-curves. The electronic band structure and, total and partial density of states of these compounds have been computed and analysed. The phonon dispersions curves of LuSe and LuTe for B2 phase are computed using density functional perturbation theory (DFPT) with generalized gradient (GGA) approximations. We also used the quasiharmonic approximation to calculate some thermodynamic properties such as constant-volume specific heat capacity of the B2 phase of LuS and LuTe compounds.

We present ab initio calculations of the structural, electronic structures, elastic, thermodynamic and vibrational properties of the Ir3Hf compound in the L1₂ structure. The calculated lattice constants, bulk modulus, and first-order pressure derivative of the bulk modulus are reported for the L1₂ structure and compared with the earlier values. The elastic constants (C₁₁, C₁₂ and C₄₄) in L1₂ phase for Ir₃Hf compound is calculated using the energy-strain method. The calculated elastic constants satisfy the mechanical stability criterion. Electronic band structures and partial and total densities of states have been derived for Ir₃Hf. The band structures show metallic character; the conductivity is mostly governed by Ir 5d states. The phonon-dispersion curves and phonon total density of states based on the linear-response method have been investigated for this compound. Temperature variations of specific heat capacity in the range of 0–1000 K are obtained using the quasi-harmonic model.

The structure, electronic, elastic and vibrational properties of the Cu₂TMAl (TM=Sc, Ti, Cr) Heusler compounds have been investigated in detail by employing an ab initio pseudopotential method and a direct method within a generalized gradient approximation (GGA-PBE) of the density-functional theory (DFT) scheme. Calculated lattice parameter values are in excellent agreement with recent experiments. In the present study, Cu₂ScAl and Cu₂TiAl does not show any magnetic moments, whereas the Cu₂CrAl has magnetic moment of 2.95 μB per formula unit. From electronic band structures we have found that these compounds have a metallic nature. The elastic constants Cij are computed using the total energy variation versus strain technique. The calculated elastic constants and bulk modulus are reported and compared with earlier available theoretical calculations. Phonon frequency for Cu₂TMAl (TM=Sc, Ti, Cr) Heusler compounds have been computed and plotted along with high symmetry directions.