Effects of mechanical and electronic properties for B2 FeAl modified by several kinds of point defects: First-principles study

Elastic, fracture and deformation behavior of B2 FeAl intermetallics modified by ternary additions as well as Al/Fe vacancy defects and anti-sites have been investigated based on density functional theory (DFT). Formation enthalpy indicates that ternary additions Sc, Y, Mo and W have a preference for Al site. While Fe site is more easily replaced by ternary Cu and Zn. Moreover, vacancy and antisite defects can be stable in FeAl. Pugh criteria ([Formula: see text] ratio), Poisson’s ratio [Formula: see text] and Cauchy pressure show that Sc, Y, Mo, W and Al vacancy (Al anti-site by Fe atom) can effectively improve the ductility of FeAl. Dislocation emission and micro-cracks propagation show that the improved ductility is due to the promoted dislocation emission but suppressed micro-cracks propagation. Bonding analyses reveal that the improved ductility is mainly own to the weakened the covalent interactions and strengthened the metallic interactions.

Probing the Structural, elastic, electronic and Thermoelectric Properties of C15-type Laves phase LaCo2: A DFT based ab-initio investigation

Using first-principles calculations based on density functional theory, structural, elastic, electronic and thermoelectric properties of laves phase LaCo2 intermetallic compound with prototype MgCu2 are stated in this paper. The optimized lattice constant by structural optimization is found to be rationally compatible with the experimental lattice constant. The Generalized Gradient Approximation (GGA) +Hubbard model was incorporated to evaluate the exact electronic structure. Elastic properties such as, elastic constants, bulk modulus B, shear modulus G, Young’s modulus E, and Poisson ratio ν have been determined using the Voigt–Reuss– Hill approximation. The ductility nature appears in both values of Cauchy pressure and Pugh’s ratio. The band structures and the Cauchy pressure show that the material behaves as metallic. In addition, semi-classical Boltzmann theory is used to verify the applicability of the material for thermoelectric applications. Calculations depict that the spin-up/down transport coefficients are temperature-dependent. It has been found that LaCo2 has a high Seebeck coefficient and therefore a large power factor.

Probing the structural, elastic, electronic and thermoelectric properties of C15-type Laves phase LaCo2: A DFT based ab-initio investigation

Using first-principles calculations based on density functional theory, structural, elastic, electronic and thermoelectric properties of laves phase LaCo2 intermetallic compound with prototype MgCu2 are stated in this paper. The optimized lattice constant by structural optimization is found to be rationally compatible with the experimental lattice constant. The Generalized Gradient Approximation (GGA) +Hubbard model was incorporated to evaluate the exact electronic structure. Elastic properties such as, elastic constants, bulk modulus B, shear modulus G, Young’s modulus E, and Poisson ratio ν have been determined using the Voigt–Reuss– Hill approximation. The ductility nature appears in both values of Cauchy pressure and Pugh’s ratio. The band structures and the Cauchy pressure show that the material behaves as metallic. In addition, semi-classical Boltzmann theory is used to verify the applicability of the material for thermoelectric applications. Calculations depict that the spin-up/down transport coefficients are temperature-dependent. It has been found that LaCo2 has a high Seebeck coefficient and therefore a large power factor.

First principles computation of structural, electronic, magnetic and mechanical properties of new lithium based half Heusler alloys

First principles calculations have been accomplished for structural, electronic, magnetic and mechanical properties of half Heusler (HH) LiYZ ([Formula: see text], Rh and [Formula: see text], Se, Te, Sb) alloys using the density functional theory (DFT) within full potential-linearized augmented plane wave (FP-LAPW) method. To calculate the physical properties, Perdew–Burke–Ernzerhof (PBE) potential and generalized gradient approximation (GGA) are employed. The calculations are accomplished for three phases to obtain the most stable phase. The results of these calculations revealed that Type-III is the most stable of LiRhSe and LiRhSb, Type-I of LiRhAs, LiRhTe, LiRuAs, LiRuSb, LiRuSe and LiRuTe alloys. The structural optimization is obtained by plotting the graphs between minimum volume and the lowest energy of all considered alloys. The results of electronic properties including density of states (DOS) and band structures are also presented. The obtained total magnetic moment (MM) is negative for LiRhSb, LiRuSb, LiRhTe, LiRuTe, while it is positive for LiRhSe, LiRuSe, LiRhAs, LiRuAs Heusler alloys (HAs). To determine the mechanical stability, several parameters such as Poisson’s ratio, Pugh’s ratio, Lame’s coefficient, anisotropy factor, Kleinman parameter, Young’s modulus, Bulk modulus and Cauchy pressure are calculated and discussed in detail.

Effects of Al substitution by Si in Ti3AlC2 nanolaminate

Recently, a series of high-purity Ti3(Al1−xSix)C2 solid solutions with new compositions (x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) have been reported with interesting mechanical properties. Here, we have employed density functional theory for Ti3(Al1−xSix)C2 solid solutions to calculate a wider range of physical properties including structural, electronic, mechanical, thermal and optical. With the increase of x, a decrease of cell parameters is observed. All elastic constants and moduli increase with x. The Fermi level gradually increases, moving towards and past the upper bound of the pseudogap, when the value of x goes from zero to unity, indicating that the structural stability reduces gradually when the amount of Si increases within the Ti3(Al1−xSix)C2 system. In view of Cauchy pressure, Pugh’s ratio and Poisson’s ratio all compositions of Ti3(Al1−xSix)C2 are brittle in nature. Comparatively, low Debye temperature, lattice thermal conductivity and minimum thermal conductivity of Ti3AlC2 favor it to be a thermal barrier coating material. High melting temperatures implies that the solid solutions Ti3(Al1−xSix)C2 may have potential applications in harsh environments. In the visible region (1.8–3.1 eV), the minimum reflectivity of all compositions for both polarizations is above 45%, which makes them potential coating materials for solar heating reduction.

Structural Optimization and the Study of the Electronic, Mechanical, Thermodynamic and Phonon Properties of Mg2sn from First Principle

First principles pseudopotential method based on density functional theory is used to investigate the Structural, Mechanical, Phonon, Thermodynamic and Electronic properties of Mg2Sn. The equilibrium properties including lattice constant, bulk modulus, pressure derivative cohesive energy, young modulus, shear modulus were determined. The results obtained were compared with available experimental and other available results. Mg2Sn was found to be brittle in nature with a non-metallic properties as shown by the value of the Cauchy pressure of -4.03. The Phonon dispersion curve of Mg2Sn was obtained utilizing the PBE-GGA exchange-correlation potential as employed in the Vienna Ab-Initio Simulation Package (VASP) computer code. The gap separating the acoustic and the optical branch of the curve was found to be about 50cm-1 at X-point. The thermodynamic properties of the material was investigated in the temperature of 0-800K. At room temperature, the calculated value of the specific heat capacity ( ) is 71.28J/mol which is in good agreement with experimental and other results. Mg2Sn was found to a narrow gap semiconductor with an indirect bandgap of magnitude of 0.175eV.

Structural, elasto-mechanical and phonon-related properties of MnCrP: A DFT Study

The Half Heusler alloy (HHA) MnCrP has been studied theoretically for structural, elasto-mechanical and phonon properties. The structure is optimized and the calculated structural parameters are close to the literature. This optimized data is used to estimate three independent second-order cubic elastic constants [Formula: see text], [Formula: see text] and [Formula: see text]. The mechanical stability criteria are explored by these constants and further used to estimate the elastic moduli; Young’s, bulk and shear modulus. The mechanical parameters like Poisson’s ratio, Pugh’s ratio, anisotropic factor, Cauchy pressure, shear constant, Lame’s constants, Kleinman parameter are also calculated and discussed. Discussions reveal the ductile nature, ionic behavior, anisotropic nature and mechanical stability of MnCrP. The metallic nature, compressibility, stiffness and interatomic forces of material are also described. Furthermore, the Debye temperature, where the collective vibrations shifts to an independent thermal vibrations, is also calculated. Longitudinal and transverse sound velocities are also obtained to investigate the phonon modes of oscillation. These phonon modes confirm the stability of the alloy as no negative phonon frequencies in the phonon-dispersion curves. These curves are used to estimate the reststrahlen band where light reflects 100% and the suitability of material is checked for Far Infrared (FIR), photographic, optoelectronic devices and sensors.

Hooke’s law and elastic constants

Hooke’s law and elastic constants are introduced. The symmetry of the elastic constant tensor follows from the symmetry of stress and strain tensors and the elastic energy density. The maximum number of independent elastic constants is 21 before crystal symmetry is considered, and this leads to the introduction of matrix notation. Neumann’s principle reduces the number of independent elastic constants in different crystal systems. It is proved that in isotropic elasticity there are only two independent elastic constants. The directional dependences of the three independent elastic constants in cubic crystalsare derived. The distinction between isothermal and adiabatic elastic constants is defined thermodynamically and shown to arise from anharmonicity of atomic interactions. Problems set 3involves the derivation of elastic constants atomistically, the numbers of independent elastic constants in non-cubic crystal symmetries, Cauchy relations, Cauchy pressure, invariants of the elastic constant tensorand compatibility stresses.

Structural and elastic properties, Vickers hardness and Debye temperature of (B1) BP: DFT study

A theoretical study of the structural parameters and elastic constants of boron phosphide (BP) compound with cubic rocksalt structure has been carried out using ab-initio density functional theory (DFT) and density functional perturbation theory (DFPT) calculations based on the plane-wave and pseudopotential (PW-PP) approach. Elastic anisotropy factors, Cauchy pressure, inverted Pugh’s ratio, aggregate mechanical moduli (shear modulus, Young's modulus and Poisson's ratio), Vickers hardness HV, elastic wave velocity as well as the Debye temperature θD and the melting point have been also calculated. Our obtained results are in general in good agreement with other data of the literature. The deviation between our obtained value (4.225 Å) of the lattice constant and the theoretical value (4.282 Å) of the literature is around 1.33%, while that between our obtained value (169.7 GPa) of the bulk modulus and the theoretical one (171 GPa) is only around 0.77%. The calculated values of HV and θD were found at around 30.5 GPa and 1254 K (1314.4 K), respectively.

Influence of pressure on electro-mechanical properties of SrNbO3: A DFT study

In the enclosure of density functional theory along with GGA (generalized gradient approximation), incorporated in Wien2k code has been utilized to explore structural, electronic and mechanical properties of SrNbO3 (SNO). It has been found that spin-polarized phase of SNO is most stable at 60 GPa with the calculated lattice constant of 3.801 Å. The calculated lattice constant and bulk modulus at 0 GPa are found to be in agreement with literature. The present calculations predict that SNO is stable and antiferromagnetic in nature up to 60 GPa. The calculated charge density contours and Cauchy pressure depicts majority of the bonding nature between the content atoms of SNO is ionic with a small contribution of covalent bond. The band-gap is found traverse from indirect R-Г gap under 0 GPa to wider direct Г-Г gap under 60 GPa. Furthermore, calculated elastic constants, C11, C12 and C44 suggest that compound is stable up to 60 GPa and exhibits ductile, anisotropic nature. Beneficial electronic and mechanical applications are predicted for SNO that could be used in optoelectronic applications.