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•The magnetization of these quaternary Heusler comes mainly from the 3d electrons of the Fe, Co, Mn and Cr atoms.•The increase in temperature for the spin up case reduces the figure of merit and increases the total electronic conductivity in these quaternary Heusler.•The resistivity of studied quaternary alloys is little sensitive to the temperature.

By first-principles calculations with density functional theory and a pseudopotential approach, the structural, electronic, and optical properties of the anhydrous 4C16H10Br2O2Bis (2-Bromobenzoyl) Methane crystals in Pbnc(N°60) and P21/c(N°14) space group are investigated. All computations are determined by a generalized gradient approximation, local density approximation and an ultra-soft pseudopotential. The calculated equilibrium parameters are in good agreement with their available experimental data. This calculation shows that the GGA/PW91 functional overestimate the lattice constant, unlike the LDA/CA-PZ. The Br–C bond distance of 1.856 (1.902) Å is comparable with experimental value of 1.901 (1.896) Å in Pbnc(P21/c) space groups. The direct band gap nature is obtained for both space groups Pbncand P21/c, since the maximum of the valence band and the minimum of the conduction band are both situated at the YA center.

•Some physical properties of SrXO3(M = Th, Zr) compounds have been investigated.•The structural parameters and elastic constants agree well with the available data.•Effect of pressure on the band gaps and some optical constants is predicted.

•The lead free halides double perovskites show a weaker resistance to compression along the principal a-axis.•The weaker resistance to volume change by applied pressure and the directional bonding between atoms.•The band structure indicates that Cs2AgBiX(X = Br, Cl) are X–Lindirect gap semiconductors.

•The negative energies of formation for all the systems indicate their stability.•The PDOS is dominated by the Fe(3–4)N-3d states.•The down-spin Fe(3–4)N-3d states dominate the antibonding region.

•Both phases of Fe7C3are classed as hard materials.•The majority of all the calculated parameters are predictions.•All the thermal properties are predictions.•We studied the temperature and pressure effect on some properties.

The functionals mBJ-LDA and mBJ-GGA result in high band gaps. BiGaO3contains covalent bonds due to the mixing of O 2pstates with the Bi and Ga s,pstates. The Bi breadth PDOS was obviously less in the valence band region compared to Ga and O, with fewer peaks than there were for Ga and consequently Ga-O hybridization is more powerful than Bi-O hybridization. All optical spectra obtained by using mBJ-GGA and EV-GGA approaches have the same profile. At the same energy as the indirect M-X band gap values of 2.24 and 2.56 eV for EV-GGA and mBJ-GGA, the imaginary component reaches non-zero magnitude. The increase in temperature from 300 to 800 K reduces the Seebeck coefficient in BiGaO3from (3000 to 1500) μV/K. As p-type and n-type ZT have similar values, BiGaO3has the same thermoelectric efficiency whether it is p-type or n-type.

This work presents the experimental results of the differential scanning calorimetry (DSC), hardness measurements (Hv) and X-ray diffraction (XRD) analysis, investigating the kinetics of precipitation phenomena in Al-7 wt % Mg alloy. In the XRD and DSC curves indicates the formation of the intermediate precipitation of β-(Al3Mg2) phase respectively. The activation energies associated with the processes have been determined according to the three models proposed by Kissinger, Ozawa and Boswell. Consequently, the nucleation mechanism of the precipitates can be explained. These phases are confirmed by the XRD analysis.

We present calculations of the structural, elastic and electronic properties of nonferrous Ti, Zr, and Hf pure metals in both parent and martensitic phases in bcc and hcp structures respectively. They are based on the generalized gradient approximation (GGA) within the density functional theory. The shear modulus, Young's modulus and Poisson's ratio for Ti, Zr, and Hf metals have were calculated and compared with the corresponding experimental values. Using elastic constants obtained from calculations under the GGA, the bulk modulus along the crystallographic axes of single crystals is calculated. This is in good agreement with experiment for Ti and Zr, whereas the hcp structure for Hf is a prediction. At zero temperature and zero pressure, the bcc crystal structure is found to be mechanically unstable for Ti, Zr, and Hf. In our calculations the hcp structure is correctly found to be stable at the equilibrium volume. In the electronic density of states, the smaller n(EF) is, the more stable the compound is, in agreement with the results obtained from the total energy minimum.

The structural, electronic and elastic properties of the M2SiC phases were studied, where M are 3d, 4d, and 5d early transition metals. The valence electron concentration (VEC) effect of Ti, V, Cr, Zr, Nb, Mo, Hf, Ta and W on these properties was examined. The C44saturates for a VEC value in surrounding of 8.5 for each serie. Hf-s, Ta-s and W-s electrons mainly contribute to the density of states at the Fermi level, and should be involved in the conduction properties. The distortion increases with increasing VEC and decreasing kc/kafactor except for the series M=Ti, V and Cr, where it is lower at the VEC value of 8.5 (it follows a parabolic variation). The M2SiC was characterized by a profound anisotropy for the shear planes (1010) and compressibility in the direction is higher than that along the cone except for W2SiC, where it is lower.

The C14H12Br2S3molecule has twofold imposed crystallographic symmetry in the solid state. 2C14H12Br2S3Bis (2-Bromobenzyl) trisulfide in the orthorhombic structure with space group P21212 is described and compared with other similar compounds. The structural, electronic, and optical properties of the anhydrous orthorhombic 2C14H12Br2S3Bis (2-Bromobenzyl) trisulfide crystals were treated within LDA/CA-PZ, GGA/PBE and GGA/PW91 approaches. The lattice parameters calculated with LDA/CA-PZ (a= 12.651 Å, b= 12.881 Å and c= 4.992 Å) are in better agreement with experimental values, where the error is 0.90 %, 1.14 %, and 4.79 % for a cutoff energy 240 eV. This calculation shows the usual trends, where the GGA/PBE and GGA/PW91 functional overestimate the lattice constant, unlike the LDA/CA-PZ. The C14H12Br2S3molecule has a large indirect band gap Z→Γ of 3.4498 eV and 3.5319 eV computed within LDA/CA-PZ and GGA/PBE approaches. The hybridization in the upper valence band between S: p, B: p and C: p, translates their covalent bonding. The Mulliken population charges show the zwitterionic state of the C14H12Br2S3molecule.

The GGA functional PW91 were used in order to predict the structural, electronic, optical and elastic properties of α and β of d- Glucose. Such compounds, in their solid form, are widely used in chemical and pharmaceutical industry. The pure crystalline forms of glucose α-d-glucose and β-d-glucose have the same space group (McDonald and Beevers, 1950) [1]. We note that despite the fact that the two compounds have the same space group, upon cooling, the interatomic distances change and a new compound occurs. On the other hand, the cooling also influences the physical properties (structural, elastic, electronic and optical properties). The objective of this paper is associated with the control of the physical states of molecular materials when they are subjected to polymorphic changes. The laws and physical parameters that govern these transformations remain fundamentally misunderstood.