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The first-principle calculations of density functional theory were used to study the structural, electronic, magnetic, mechanic, and half-metallic behavior of Y2MnZ (Z = Al, Ga, In) within the spin generalized gradient approximation. These compounds can be experimentally synthesized due to their negative values of the calculated formation energies. Our calculations indicate that they are more stable in Cu2MnAl-type structure. The Hg2CuTi-type structure displays half-metallic characteristic with 100% spin polarization at the Fermi level. The value of calculated magnetic moment has an integer value of 2μB for Y2MnZ (Z = Al, Ga, In) in the Hg2CuTi-type structure which well matches with magnetic moments predicted from Slater–Pauling rule. Therefore, the Y2MnZ (Z = Al, Ga, In) in the Hg2CuTi-type structure is predicted to be a candidate for possible spintronics applications. [ABSTRACT FROM AUTHOR]

Spin-coating technique is employed to deposit nanostructured zinc oxide (ZnO) doping aluminium (Al) on p-Si substrate. Atomic forces microscopy (AFM), X-ray diffraction (XRD), ultraviolet–visible (UV–Vis) and scanning electron microscopies (SEM) are utilized to investigate the influence of annealing temperature in the range of 200 to 600°C on the morphological, optical, structural and topographical characteristics of Al NPs-doped ZnO (AZO) nanostructure. The average reflectance is proven by the reflectance spectra to be in the wavelength range of 200–1000 nm, and the absorption spectra provided the optical energy gaps of nanostructured AZO. Crystalline and grain size are correlated with annealing temperature variations, thus providing more homogeneous and covered surface morphology. Our results are nominated for future researches. [ABSTRACT FROM AUTHOR]

Mn-Ni based full-Heusler alloys belong to novel half-metallic compounds with a promising set of physical properties for applications as functional materials. Based on first principles calculations, the electronic structures, the magnetic and mechanical properties of Ni2Mn(Ge,Sn) and Mn2NiGe full-Heusler alloys have been investigated in detail. The results revealed that the Mn2NiGe with Hg2CuTi type structure is more stable; on the other hand, for Ni2Mn(Ge,Sn), the Cu2MnAl type structure is more stable. The Mn2NiGe alloys are found to be half-metallic with an integer value of total magnetic moment of 4 μB which makes them interesting materials in the field of spintronics. The Ni2Mn(Ge,Sn) alloys exhibit metallic character in both Hg2CuTi and Cu2MnAl type structures. The calculated B/G ratios for all the considered compounds Ni2Mn(Ge,Sn) and Mn2NiGe are greater than 1.75; therefore, these alloys are ductile, and the calculated Cauchy's pressure is positive, which also classified these compounds as ductile materials. [ABSTRACT FROM AUTHOR]

ab-initio calculations are employed to determine the structural, mechanical, elastic, electronic and thermodynamic properties of perovskite oxides XTcO 3 (X = K, Rb). From the computed structural properties, KTcO 3 and RbTcO 3 are found to be stable with equilibrium lattice constants; 7.3943 Bohr and 7.4909 Bohr, respectively. From electronic structure results, a metallic character is remarked for both compounds. The determined elastic constants (C 11 , C 12 , C 44) have indicated the mechanical stability of XTcO 3 (X = K, Rb) compounds that is confirmed by the phonon spectra. In addition, KTcO 3 is found to be isotropic and KTcO 3 is nearly isotropic according the anisotropic constant A values. B/G ratio has indicated the brittleness of both compounds. Furthermore, the Helmholtz free energy (F), entropy (S) and heat capacity (C V) are determined using QHA (Quasi harmonic Approximation). Our computational indicates that XTcO 3 (X = K, Rb) compounds can be used as new materials for solid oxide fuel cells and related applications. [ABSTRACT FROM AUTHOR]

In this work, based on first-principle calculations, the structural, mechanical and phonons properties of binary intermetallic compound BaSn 3 have been studied through the PBEsol-GGA scheme in the framework of DFT. The ground-state properties such as bulk modulus (B), pressure derivative (B 0), the lattice constants (a 0 , c 0), bond-lengths and unit cell volume are presented in detail from 0 GPa to 100 GPa. The results show a significant impact of the pressure on these parameters, and the axial compressibility along the c axis is always stiffer than the a-axis. Our calculations are in accord with the previously measured ones which prove the validity and the accuracy of the chosen theoretical approach. Furthermore, polycrystalline elastic constants, the single-crystal, and its pressure dependence are numerically predestined. After analyzing the calculated elastic constants, it is shown that this compound is mechanically stable over the pressure range of 0 GPa–100 GPa and shows a very weak resistance to elastic shear deformation. The mechanical properties obtained from the calculated values of elastic constants and its relevant quantities, such as hardness parameter Hv , bulk modulus B, Young's modulus E , shear modulus G , have been reported. The dependence of the elastic constants C ij , the aggregate B , G moduli, and the anisotropies on pressure have been investigated. Moreover, the calculated value of Young's and shear moduli affirms the softening behavior of this material. Besides, brittleness/ductility for BaSn 3 is further estimated by calculating the ratio of B/G , Poisson's ratio and Cauchy pressure. Among the intermetallic compound, BaSn 3 is found to be a brittle system at the low pressure whereas it exhibits ductile deformation behavior at high pressure. Furthermore, the mechanical anisotropy proved by analyzing several anisotropy indexes (A 1 , A U , A 3 ,..) , 3D curved surface of Young's moduli that this compound is elastically anisotropic, and strongly pressure dependent. The Debye temperature is also obtained from calculating the mean elastic wave velocity in different directions of the single crystal. We also performed calculations for phonon dispersions at high pressure. It's found that this structure is dynamically stable under pressure. • BaSn 3 compound is an intermetallic compound that exhibits metallic properties. It is very interesting in the chemistry and materials community due to its complex structure and weakly bonded atoms. • Mechanical and phonons properties of this compound have not taken attention in previous theoretical or experimental studies. • The BaSn 3 structure is shown to be mechanically and dynamically stable under pressure. • BaSn 3 is relatively anisotropic material and the pressure can make it more anisotropic. • BaSn 3 is found to be a brittle system at the low pressure whereas it exhibits ductile deformation behavior at high pressure. [ABSTRACT FROM AUTHOR]

• Binary BaSn 3 is an intermetallic compound that exhibits metallic character. It is very interesting in the chemistry and materials community due to its complex structure, good electronic conductivity, and strongly bonded atoms. • Related optical and some electronic properties of this compound have not taken attention in Previous theoretical or experimental studies. • BaSn 3 compound presents anisotropy between the optical components in the [100], [101] and [001] polarization directions. • BaSn 3 should be more conductive in the visible energy region and changes from a metallic to the dielectric response if the incident light has a frequency greater than the plasma frequency. • BaSn 3 compound has wider absorptive transitions in the visible region. The electronic and optical properties of intermetallic compound BaSn 3 are investigated at high pressure from the first principles density functional theory calculations using the plane-wave pseudo-potential method within generalized gradient approximations in the forms of PBEsol (PBEsol-GGA). Furthermore, the electronic properties such as band structure, the total and partial densities of states have been computed and assessed in comparison with the existing studies. Meanwhile, the calculated band structures demonstrate that this compound has a metallic character. In addition to that, the electronic structures were discussed to reveal the bonding characteristics, and the electronic charge density plots show the presence of covalent with partial ionic bonding in this compound. On the other hand, an accurate calculation of frequency-dependent polarized optical functions (including the dielectric function, refractive index, birefringence extinction coefficient, absorption coefficient, also reflectivity and energy-loss function spectra) were performed and presented in the energy range 0–20 eV. The results obtained are discussed within the frame of available information on the electronic band structure of this compound. We can conclude that the optical spectra exhibited a relative optical anisotropy in different polarizations of the incident light along [100], [111] and [001] crystallographic directions. On the top of that, the optical conductivity of BaSn 3 was also determined. [ABSTRACT FROM AUTHOR]

In this manuscript, the electronic structure, bonding nature and optical properties of the ternary Ba2HgS5 compound was investigated using the density functional theory (DFT). The generalised gradient approximation (GGA), Engel and Vosko generalised gradient approximation (EV-GGA) and the modified Becke Johnson (mBJ) schemes were used to model the exchange and correlation potentials. Band structure calculations indicate that this compound has a direct energy band gap value of 2.34 eV, showing a close agreement with the experimental band gap value of 2.40 eV. The energy band gap value calculated using the mBJ formalism is larger than those obtained from the GGA and the EV-GGA approaches. From the analysis of the partial electronic energy density of states, it was observed that the valence band is dominated by the Ba-p, S-s and Hg-d electronic states, while the conduction band is formed by the S-p and Ba-d orbitals. In addition, there exists a strong hybridisation in the valance band and in the conduction band between the S-p and Hg-s, Ba-s and Hg-f, Hg-s, S-p as well as the S-p and Hg-p states, respectively. This strong hybridisation leads to strong covalent bonding between the Hg-S and Ba-S atoms. Moreover, the optical constants were calculated and discussed in details. The energy dependent optical parameters were found to be anisotropic with respect to the polarisation of the incident electromagnetic wave and exhibit features in complete agreement with the electronic band structure calculations. The compound absorbs ultraviolet radiation quite strongly. Ba2HgS5 possesses high refractive index over a wide range of frequency and has potential to be used as anti-reflective coating and also in photonic devices like in light emitting diodes (LEDs). [ABSTRACT FROM AUTHOR]

We performed ab initio calculations to study the structural and optoelectronic properties of simple and slab phase TaNO using density functional theory (DFT), in which the full potential augmented plane wave (FP-LAPW) method was implemented using the computational code Wien 2k. The modified Becke-Johnson potential (mBJ-GGA) was used for these calculations. The calculated band structure and electronic properties revealed an indirect bandgap for simple TaNO (3.2 eV) and a direct bandgap for slab TaNO (1.5 eV). The interband electronic transitions were investigated from the band structure, and transition peaks were observed from the imaginary part of the dielectric function. These transitions are due to Ta-p, N-p and O-p orbitals for simple TaNO and Ta-p, N-s as well as O-p orbitals for slab TaNO. The plasmon energy was related to the main peak of the energy loss function, which was approximately 10 eV. The static value of the dielectric constant and the refraction were close to the experimental values. In general, slab TaNO shows different properties and is more suitable for optoelectronic applications due to direct bandgap. Image 1 • DFT calculations of the structural and optoelectronic properties for bulk and slab phase TaNO. • The electronic properties reveals a direct (indirect) band gap for slab (simple) TaNO. • The interband electronic transitions are investigated by band structure. • Slab TaNO shows different properties and is more suitable for optoelectronic applications. [ABSTRACT FROM AUTHOR]

Abstract To investigate the structural, elastic and electronic properties of the tetragonal inter-alkali metal chalcogenides CsNaX (X = S, Se, and Te), we have applied the full-potential linearized augmented plane-wave plus local orbital (FP-LAPW + lo) method within the density functional theory (DFT) framework. For the description of the exchange-correlation potential, the Wu-Cohen generalized gradient approximation (WC-GGA) was employed. Furthermore, the generalized gradient approximation of Engel and Vosko (EV-GGA) and Tran-Blaha modified Becke-Johnson (TB-mBJ) potential were also applied to obtain reliable results for the electronic properties of CsNaX compounds. Our optimized equilibrium structural parameters are in good agreement with experimental measurements where available. The Young's modulus, bulk modulus, shear modulus, Poisson's ratio, Pugh's ratio, acoustic velocities and Debye temperature were derived from our estimated elastic constants C i j. It is found that all the considered compounds are mechanically stable and ductile in nature. In addition, the elastic anisotropy of the examined compounds was studied by visualizing the directionally dependent Young's modulus, shear modulus and compressibility, as well as by calculating some elastic anisotropy indices. Electronic properties, such as the band structure, density of states and the charge density, were analyzed in detail. Calculated band structures show that the studied materials are semiconductors with indirect band gaps (Z-Γ). Highlights • Some physical properties for CsNaX (X = S, Se, Te) compounds are investigated. • Calculated lattice constants parameters compare well with experimental data. • Studied compounds are indirect gap materials. • Elastic and electronic properties for the compounds are predicted for the first time. [ABSTRACT FROM AUTHOR]

The structural, electronic, optical and thermodynamic properties of the Al x In 1- x N ( x  = 0, 0.25, 0.50, 0.75 and 1) ternary alloys were investigated using the full potential linearized augmented plane wave (FP-LAPW) method in the framework of density functional theory (DFT). Optimized lattice parameter, bulk modulus and its pressure derivative were determined from suitable fit of the total energy versus volume with Murnaghan equation of state (EOS) for all considered alloys. Variations of the lattice parameter and bulk modulus with the Al concentration ( x ) deviate from Vegard’s law. Electronic band structure, dielectric function and refractive indices were investigated and computed for the considered alloys. It is found that the variations of the band gap, the static dielectric constant and static refractive index versus the Aluminum Al concentration obey to a quadratic polynomial. Temperature and pressure dependencies of the Gibbs free energy G , isochoric heat capacity C V , entropy S and Debye temperature θ D were investigated via the Debye quasi-harmonic model for the Al 0.5 In 0.5 N ternary alloy. Furthermore, the elastic constants C ij , the bulk modulus B, Shear modulus G with Young modulus E and the Poison’s ratio v with the compressibility B/G were carried out in the cubic phase. Deduced results agree well with the available theoretical and experimental results. [ABSTRACT FROM AUTHOR]

We have studied the structural, optical, electronic and thermoelectric properties of the CaCd 2 X 2 (X = P, As) compounds by using the full-potential augmented plane wave plus local orbitals method (FP-APW + lo). The exchange-correlation potential was treated using both the gradient generalized approximation (WC-GGA) and local density approximation (LDA). The estimated structural parameters, including the lattice parameters and internal coordinates agree well with the available experimental data. Our computed band structure shows that both studied compounds are semiconductors, with direct band gaps (Γ-Γ) of approximately 1.78 eV and 1.2 eV for CaCd 2 P 2 and CaCd 2 As 2 , respectively, using GGA-TB-mBJ approach. The calculated optical spectra reveal a strong response of these materials in the energy range between the visible light and extreme UV regions, making them a good candidate for optoelectronic devices. Thermoelectric parameters, such as thermal conductivity, electrical conductivity, Seebeck coefficient, power factor and figure of merit were calculated. We note that both the CaCd 2 P 2 and CaCd 2 As 2 compounds show promising thermoelectric properties. [ABSTRACT FROM AUTHOR]

Ab initio calculations were performed to investigate the structural, elastic, electronic and optical properties of the ternary layered systems A InS 2 ( A  = K, Rb and Cs). The calculated structural parameters are in good agreement with the existing experimental data. Analysis of the electronic band structure shows that the three studied materials are direct band-gap semiconductors. Density of states, charge transfers and charge density distribution maps were computed and analyzed. Numerical estimations of the elastic moduli and their related properties for single-crystal and polycrystalline aggregates were predicted. The optical properties were calculated for incident radiation polarized along the [100], [010] and [001] crystallographic directions. The studied materials exhibit a noticeable anisotropic behaviour in the elastic and optical properties, which is expected due to the symmetry and the layered nature of these compounds. [ABSTRACT FROM AUTHOR]

Our present article reports the carbon substitution-driven changes in the behavior of BeSi 1- x C x P 2 and BeGe 1- x C x P 2 (x = 0.25 and 0.5) chalcopyrite alloys using the full-potential augmented plane wave plus local orbital (FP-APW + lo) based first-principles calculations. The lattice constants (a and c) of BeSi 1- x C x P 2 and BeGe 1- x C x P 2 are shortened, and the bulk moduli are improved as carbon atoms replace Si and Ge atoms. The computed negative formation energy (E f) indicate adequate thermodynamic stability of the BeSi 1- x C x P 2 and BeGe 1- x C x P 2 alloys. The bandgaps pristine BeSiP 2 and BeGeP 2 computed as 1.84 eV and 1.54 eV, respectively, using the modified Tran-Blaha (TB) Becke Johnson (mBJ) transition potential, matching well to the experimental results. However, the C substitution is found to narrow the bandgap of BeSiP 2 and BeGeP 2 considerably. Similarly, C substitution is found to reduce electrons' and holes' effective mass and enhance the absorption coefficient of BeSi 1- x C x P 2 and BeGe 1- x C x P 2 alloys up to (α ∼ 10 5 c m − 1 ). Our predictions indicate that the physical properties of BeSiP 2 and BeGeP 2 chalcopyrite can be modified effectively by replacing C in the Si and Ge sites, which makes them promising for optoelectronic applications. Lattice parameters and bulk modulus versus C concentration of BeSiP 2 and BeGeP 2. [Display omitted] • Some physical properties of C doped BeSiP 2 and BeGeP 2 chalcopyrite are investigated. • The calculated electronic and optical properties of pure BeSiP 2 and BeGeP 2 compare well with the available data. • The substitution of carbon decreases the value of bandgaps, hole and electron masses. • Doping BeSiP 2 and BeGeP 2 enhance the absorption in visible light making them promising for optoelectronic applications. [ABSTRACT FROM AUTHOR]

We report ab initio density functional theory calculations of the structural, elastic, electronic and optical properties of the double perovskite oxides Sr 2 AlXO 6 (X=Ta, Nb, V). We have predicted a direct Г–Г band gap in Sr 2 AlXO 6 (X=Ta, Nb) and an indirect Г–X band gap for Sr 2 AlVO 6 . The fundamental band gap increases linearly when the pressure is enhanced in the range 0–20 GPa. The frequency dependent of complex dielectric function, absorption, reflectivity and electron energy loss function were investigated in the range 0–40 eV. Features such as lattice constant, bulk modulus, elastic constants, band structure, total and local densities of states have been computed. [ABSTRACT FROM AUTHOR]

The indirect energy gap ( Γ − X ) is calculated using density functional theory (DFT) of the full potential-linearized augmented plane wave (FP-LAPW) method as implemented in WIEN2K code. The Engel–Vosko generalized gradient approximation (EV-GGA) formalism is used to optimize the corresponding potential for energetic transition and optical properties calculations of CdS 1− x Te x alloys as a function of quantum dot diameter and is used to test the validity of our model of quantum dot potential. The refractive index and optical dielectric constant are investigated to explore best applications for solar cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • Based on DFT calculations, the XFeGe (X = Co, Cr, Ni) half Heusler alloys were investigated. • Half metallic behavior is explained via spin polarization results. • Magnetic and electronic properties for the XFeGe (X = Co, Cr, Ni) were studied. • The calculated elastic constants for the three compounds verified the mechanical stability criteria for cubic systems. The structural, electronic, magnetic and thermodynamic properties of XFeGe (X = Co, Cr, Ni) half Heusler compounds are studied using first-principles calculation within density functional theory in five different atomic configurations. For each configuration, their optimized lattice constants are determined. It showed that the configuration of type 3 is energetically the most stable. From the spin-polarized band structure and density of states, it is found that CoFeGe alloy exhibits a half-metallic character with integer magnetic moments of 3.00μ B per formula unit at their equilibrium volume, whereas NiFeGe and CrFeGe exhibit a metallic character. These results indicate that the magnetic moment mainly originates from the Fe atoms. The calculated equilibrium volume for the three compounds CoFeGe, CrFeGe, and NiFeGe at various temperatures is predicted. The heat capacity at constant volumeC V has been calculated as a function of temperature and pressure. Additionally, the calculated elastic constants for the three compounds confirm the mechanical stability criteria for cubic systems. [ABSTRACT FROM AUTHOR]

Highlights: [•] The calculated structural parameters of hexagonal U3ZrSb5 are found in good agreement with the experimental data. [•] U3ZrSb5 is found to be ferromagnetic material. [•] Evident effects of the Hubbard U parameter in the uranium “5f” states are noted. [•] Our band structure calculation show the metallic behavior of this ferromagnetic compound. [•] The thermodynamic properties are predicted through the quasi-harmonic Debye model. [ABSTRACT FROM AUTHOR]

Over the years, vanadates are attracting sizable consideration of the researchers owing to their versatile functional properties. Through an ab initio computational approach, a comprehensive study was performed on terbium orthovanadate (TbVO 4); the study includes an investigation on its electronic structure, magnetic behavior, as well as mechanical and optical properties. The computations are performed by employing the "full-potential linearized augmented plane wave plus local orbital (FP-LAPW ​+ ​lo)" methodology framed with "density functional theory (DFT)". To incorporate the "exchange correlation energy/potential" functional into total energy calculations, the "Perdew-Burke and Ernzerhof" approach to "generalized gradient approximation" was employed by using WIEN2k computational code. In addition, to analyze the d-orbital electrons of vanadium (V) and the f-orbital electrons of terbium (Tb) more precisely, the GGA ​+ ​U approximation is also used. The computational obtained results of structural parameters are found to be in good agreement with the experimentally measured one. Moreover, TbVO 4 showed mechanical stability and ductility as well. The computed electronic structure reveals that TbVO 4 is a direct gap semiconductor compound with band gap energy comparable to that of the experimentally one. The magnetic moment and density of states results confirm that TbVO 4 is an antiferromagnetic material. For completeness, the optical and mechanical anisotropy are also simulated and analyzed. [Display omitted] • Some Physical properties for tetragonal TbVO 4 in its antiferromagnetic state are investigated. • The calculated ground states properties for TbVO 4 compare well with the available data. • The electronic properties calculation reveals that this compound is wide-direct band gap. • The mechanical, optical and magnetic characteristics for TbVO 4 are investigated for the first time. [ABSTRACT FROM AUTHOR]

Abstract: The alkaline platinum hydrides are considered the most promising as hydrogen storage materials. The alloying ability of crystal, elastic constants and related parameters, electronic and optical properties have been studied using pseudo-potential plane–wave method based on the density functional theory. The investigated compounds show a weaker resistance to compression along the principal a-axis and their resistance to shear deformation is lower than the resistance to the unidirectional compression. The band structure indicates that A2PtH6 (A=K, Rb and Cs) are X–X direct gap semiconductors. The effective electron mass at equilibrium has been predicted towards X–Γ, X–W and L–W directions. The strong hybridization between Pt-d and H-s states in the upper valence band translates the existence of covalent bonding character in these compounds. The static optical dielectric constant is inverse proportional to the fundamental gap. [Copyright &y& Elsevier]

Abstract: Li2PtH6 and Na2PtH6 are good candidate for hydrogen storage. The structural, elastic, electronic and optical properties of Li2PtH6 and Na2PtH6 compounds have been investigated using pseudo-potential plane–wave method based on the density functional theory. Computed lattice constant and H atom positional parameter at equilibrium agree well with the available experimental data. A quadratic pressure dependence of the elastic stiffness is found. A set of isotropic elastic parameters and related properties, namely bulk and shear moduli, Young''s modulus, Poisson''s ratio, average sound velocity and Debye temperature are numerically estimated in the framework of the Voigt–Reuss–Hill approximation for Li2PtH6 and Na2PtH6 polycrystalline aggregate. The analyses of the band structure indicates that Li2PtH6 and Na2PtH6 are indirect gap semiconductors. The static dielectric constant and static refractive index are inversely proportional to the fundamental gap. [Copyright &y& Elsevier]

Abstract: The chemical bonding of the ZnAl2Se4, CdAl2Se4 and HgAl2Se4 defect chalcopyrites has been studied in the framework of the quantum theory of atoms in molecules (AIM). The GW quasi-particle approximation is used to correct the DFT-underestimation of energy gap, and as a consequence the linear and nonlinear optical properties are significantly enhanced. The second harmonic generation (SHG) displays certain dependence with the ionicity degree decrease through the dependency of the SHG on the band gap. The occurrence of the AIM saddle point is characterized and some clarifying features in relationship with the density topology are exposed, which enable to understand the relation with the second harmonic generation effect. [Copyright &y& Elsevier]

Abstract: A theoretical study of the structural, electronic, optical and thermodynamic properties of Na x Rb1−x H and Na x K1−x H ternary alloys in NaCl phase has been carried out using the first-principles method. We modeled the alloys at some selected compositions with ordered structures described in terms of periodically repeated supercells. The dependences on the composition of the lattice constant, band gap, dielectric constant, refractive index, Debye temperature, mixing entropy and heat capacities were analyzed for x=0, 0.25, 0.50, 0.75 and 1. The lattice constants of Na x Rb1−x H and Na x K1−x H exhibit a marginal deviation from Vegard''s law. A strong deviation of the bulk modulus from linear concentration dependence was observed for both alloys. We found that the composition dependence of the energy band gap is highly non linear and the large bowing coefficient for Na x Rb1−x H is sensitive to the composition. Using the approach of Zunger and co-workers, the microscopic origins of the gap bowing were detailed and explained. The thermodynamic stability of these alloys was investigated by calculating the phase diagram. The thermal effect on some macroscopic properties was investigated using the quasi-harmonic Debye model. There is a good agreement between our results and the available experimental data for the binary compounds, which is a support for those of the ternary alloys that we report for the first time. [Copyright &y& Elsevier]

Abstract: The structural, elastic, electronic and thermal properties of the MAX phases Ti 2 SiC and Cr 2 SiC are studied by means of the pseudo-potential plane wave method within GGA and LDA. The effect of pressure on the normalized lattice constants a/a 0 and c/c 0 and the internal parameter z is investigated. Our results of elastic constants, sound velocities and Debye temperature are predictions. The Ti 2 SiC and Cr 2 SiC compounds behave as ductile material and show a stronger anisotropy. The analysis of the band structure and density of states show that these compounds are electrical conductors, having a strong directional bonding between Ti and C and Cr and C atoms assured by the hybridization of Ti–d and Cr–d atom states with C–p atom states. The thermal effect on the primitive cell volume, bulk modulus, heat capacities CV and CP were predicted using the quasi-harmonic Debye model. [Copyright &y& Elsevier]

Abstract: The structural, elastic, electronic, and optical properties of cubic spinel MgIn2S4 and CdIn2S4 compounds have been calculated using a full relativistic version of the full-potential linearized-augmented plane wave with the mixed basis FP/APW+lo method. The exchange and correlation potential is treated by the generalized-gradient approximation (GGA). Moreover, the Engel–Vosko GGA formalism is also applied to optimize the corresponding potential for band structure calculations. The ground state properties, including the lattice constants, the internal parameter, the bulk modulus, and the pressure derivative of the bulk modulus are in reasonable agreement with the available data. Using the total energy-strain technique, we have determined the full set of first-order elastic constants C ij and their pressure dependence, which have not been calculated or measured yet. The shear modulus, Young’s modulus, and Poisson’s ratio are calculated for polycrystalline XIn2S4 aggregates. The Debye temperature is estimated from the average sound velocity. Electronic band structures show a direct band gap (Г–Г) for MgIn2S4 and an indirect band gap (K–Г) for CdIn2S4. The calculated band gaps with EVGGA show a significant improvement over the GGA. The optical constants, including the dielectric function ε(ω), the refractive index n(ω), the reflectivity R(ω), and the energy loss function L(ω) were calculated for radiation up to 30eV. [ABSTRACT FROM AUTHOR]

Abstract: A theoretical study of structural, electronic, linear and nonlinear optical properties of ZnIn2Te4 defect-chalcopyrite is presented using the full-potential linearized augmented plane-wave (FP-LAPW) method. The exchange and correlation potential is treated by the generalized-gradient approximation (GGA). Moreover, the Engel and Vosko GGA formalism (EV-GGA) is also used to improve the band gap results. The lattice parameters ( a , c ) and the atomic positions (x, y and z) are optimized and found in good agreements with the available experimental data. Our calculations performed for band structure and density of state show that the valence band maximum (VBM) and conduction band minimum (CBM) are located at Γ resulting in a direct energy gap of about 0.89eV for GGA and 1.20eV for EV-GGA. The linear optical properties namely, the real and imaginary parts of the dielectric function and the reflectivity spectrum are calculated. This compound possesses a considerable negative birefringence. Based on the density functional theory the nonlinear optical properties are calculated and their spectra are analyzed. [ABSTRACT FROM AUTHOR]

Abstract: The structural, elastic, electronic, optical and thermodynamic properties of the perovskite chloride CsCdCl3 were investigated using the pseudo-potential plane wave (PP-PW) within the Generalized Gradient Approximation (GGA) and Local Density Approximation (LDA). The computed lattice parameter agrees well with experimental and previous theoretical works. Based on the elastic constants and their related parameters, the crystal rigidity and mechanical stability have been discussed. Energy band structure shows that the investigated material is indirect energy band gap semiconductor. The static dielectric constant and static refractive index are indeed, proportional to the fundamental indirect band gap. The thermal effect on the lattice parameter, bulk modulus, volume expansion coefficient, Grüneisen parameter, heat capacities and Debye temperature were predicted using the quasi-harmonic Debye model. To the best of the authors’ knowledge, most of the studied properties are reported for the first time. [Copyright &y& Elsevier]

Abstract: Structural, electronic, elastic and optical properties of the cubic-antiperovskite-type ANSr3, with A=As, Sb and Bi, are studied under pressure effect using the full-relativistic version of the full-potential augmented plane wave plus local orbitals method (FP-APW+lo). The exchange–correlation potential is treated by the generalized gradient approximation within the scheme of Perdew, Burke and Ernzerhof (GGA-PBE). Also we have used Engel and Vosko GGA formalism (GGA-EV) to improve the band gap results. The calculated bulk properties, including lattice constants, bulk moduli and their pressure derivatives are in reasonable agreement with the available data. The elastic constants Cij and their pressure dependences are calculated using the total energy-strain technique. The shear modulus, Young''s modulus, Poisson''s ratio and Lame''s coefficients are estimated in the framework of the Voigt–Reuss–Hill approximation for ideal polycrystalline ANSr3 aggregates. The Debye temperature is estimated from the average sound velocity. Energy band structures show that the investigated materials are direct energy band gap semiconductors. Analysis of the density of states and charge density distribution shows that the bonding is a mixture of covalent and ionic character. For the first time, the real and imaginary parts of the dielectric function ε(ω), the refractive index n(ω), the reflectivity R(ω) and the energy loss function L(ω) are calculated for radiation up to 18eV. [Copyright &y& Elsevier]

Abstract: A theoretical study of elastic and electronic properties of the filled skutterudite CeFe4P12 is presented, using the full-potential linear muffin–tin orbital (FP-LMTO) method. In this approach the local spin density approximation (LSDA) was used for the exchange-correlation (XC) potential. Results are given for lattice constant, bulk modulus, its pressure derivative and elastic constants. Our calculations performed for band structure and density of state show that this compound is an indirect band gap material (Γ–N). The results are compared with previous calculations and experimental data. [Copyright &y& Elsevier]

• Mn 2 SiC is ductile, whereas Mn 2 AlC is brittle. • Mn 2 AlC is a promising thermal barrier coating (TBC) material. • Mn 2 AlC and Mn 2 SiC are suitable for use in harsh environments. • Both of studied compounds remain mechanically stable under the pressure up to 30 GPa. [Display omitted] The inherent properties of MAX phases have made them candidate materials for various technological applications. From this perspective, the present article reports the results of a detailed theoretical investigation of the effects of pressure on the structural, elastic, magnetic, and thermodynamic properties of Mn 2 AlC and Mn 2 SiC MAX phases using density functional theory (DFT). The lattice parameter c decreases with increasing pressure slightly faster than the lattice constant a. Both of studied compounds remain mechanically stable under the pressure up to 30 GPa. All independent elastic constants increase non-linearly with increasing pressure. Mn 2 SiC is ductile, whereas Mn 2 AlC is brittle at ambient pressure. The ductility of Mn 2 SiC increases with increasing pressure, while Mn 2 AlC undergoes a transition from brittle to ductile at 10 GPa. It is found that Mn 2 AlC is stable in a ferromagnetic ordering of magnetic moments, while Mn 2 SiC is stable in an anti-ferromagnetic ordering. The magnetic moment of Mn in Mn 2 AlC at zero pressure is approximately 1.67 μ B , which is consistent with the value of 1.86 μ B reported in the literature. The high melting temperature and high Debye temperature of Mn 2 AlC and Mn 2 SiC make them suitable for use in harsh environments. Mn 2 AlC is a promising thermal barrier coating (TBC) material. The rate of increase of the isobaric heat capacity C p of Mn 2 AlC with increasing temperature is higher than that of Mn 2 SiC. The thermal expansion coefficient of Mn 2 AlC is larger than that of Mn 2 SiC over all pressure and temperature ranges considered here. We hope this study will inspire MAX phase researchers around the world to further explore the properties of the title materials through experiments and theories. [ABSTRACT FROM AUTHOR]

[Display omitted] • Importance of calculation based on the exchange and correlation potential TB-mBJ, revealing the electron distribution DOS in the valence band, the electron transitions in the Brillouin zone and the anisotropy character of ZnSe. • Usefulness of REELS technique, allowing to confirm the calculated electron transitions in the Brillouin zone and to identify the nature of electron states which contribute in the electron transitions from the valence band to the conduction band. • Study of electron states in the band gap of ZnSe with PL spectroscopy. Our work aims to establish a correspondence between the obtained theoretical and experimental results on the electronic and optical properties of ZnSe. The calculated DOS (Density of States) using the FP-LAPW method with the Tran-Blaha modified Becke-Johnson exchange-correlation potential reveal that the upper valence energy levels involve an important contribution from the Se-(4 p and 3 d) electron states with a small contribution from the Zn-2 s states. The real (ε 1 (ω)) and imaginary (ε 2 (ω)) parts of the dielectric function show the anisotropy character of w-ZnSe. The main peaks appearing in the ε 2 (ω) spectrum, are calculated by summing over all contributions of electronic transitions between the pairs of bands V n → C n ′ , where V n is an occupied valence band and C n′ is an unoccupied conduction band. Experimentally, the XPS (X-Ray Photoelectron Spectroscopy) analysis technique is used to show the clean and homogeneous state of ZnSe. To confirm the calculated electron transitions, we use the REELS (Reflected Electron Energy Loss Spectroscopy) technique of great sensitivity for displaying the electron interband transitions. The electron states in the w-ZnSe gap are determined through the Gaussian deconvolution of the photoluminescence spectrum (PLS). [ABSTRACT FROM AUTHOR]

To find a seemly solution to the problems of efficiency dependency of the hybrid PV/TE devices, on important factors like "high-absorbance with high-ZT materials" and improving the performance of existing devices, are essential research topics nowadays. In this regard, we report here optical coating, and thermoelectric features of the kesterite-structured Ag 2 CdSnS 4 and Ag 2 CdSnSe 4 compounds. These investigations are performed at the level of "full-potential linearized augmented plane wave plus local orbital method, FP-L(APW + lo)" framed within the "density functional theory (DFT)" method comprised with relativistic effects. Our study of the optical coating shows that both the investigated materials have a good level of absorbance (A), approximately 80% in the visible part of the spectra. Further, we found that the magnitude of reflectance (R) of the Ag 2 CdSnX 4 (X = S, Se) thin films increase with increasing film thickness, while the response of the transmittance (T) spectra is reverse to it. These results are corroborated by the study of the transport properties by employing the Boltztrap code, and correspondingly electrical conductivity, Seebeck coefficient, electronic thermal conductivity as well as the figure of merit parameters were evaluated and analyzed as a function of the chemical potential for both investigated compounds at five values of the temperatures. Hence our obtained results show that both the investigated semiconductor materials exhibit strong potential for the application of hybrid PV/TE systems. • Some Physical properties for the Ag 2 CdSnX 4 (with X = S, S e) are investigated. • The calculated ground states properties for Ag 2 CdSnX 4 (with X = S, S e) compare well with the available data. • The electronic properties calculation reveals that the compounds are direct band gap semiconductors. • The optoelectronic and thermoelectric characteristics for Ag 2 CdSnX 4 (with X = S, S e) are investigated for the first time. [ABSTRACT FROM AUTHOR]

In this work, the effect of the composition on the structural, electronic, elastic, optical and thermodynamic properties of the Ga 1-x Al x As 1-y P y quaternary alloys are investigated using the full-potential augmented plane wave plus local orbitals (FP-APW + lo) approach in the density functional theory framework as embodied in the WIEN2k computational package. The fundamental physical properties of the cubic Ga 1-x Al x As 1-y P y quaternary alloys, such as lattice constant, bulk modulus, energy band structure and elastic constants, are predicted for the first time. The obtained results show that the Ga 1-x Al x As 1-y P y quaternary alloys are direct band gap semiconductors, while their parents; GaP, AlAs, and AlP binary compounds are indirect band gap semiconductors. It is found that the studied materials are of brittle character and ionic bonding nature. The static dielectric constant and static refractive index of the considered alloys are calculated and compared with the obtained results using empirical models. Pressure and temperature dependencies of some thermodynamic parameters of the title quaternary alloys are also investigated and discussed. • Fundamental physical properties of the Ga 1-x As x Al 1-y P y quaternary alloys are determined. • The structural, properties of Ga 1-x As x Al 1-y P y alloys show the possibility of the deposition on GaAs and AlAs substrates. • The Ga 1-x As x Al 1-y P y quaternary alloys are wide band gap semiconductors and they are brittle in nature.. • The thermodynamic parameters dependences on (P,T) of the Ga 1-x As x Al 1-y P y for x=y=0.5 and x=y=0.25 are calculated. • The C V and the entropy S of the alloys are strongly affected when changing temperature at constant pressure. [ABSTRACT FROM AUTHOR]

In this paper, we present the results of a detailed computational study of the structural, electronics, optical, thermodynamic, and thermoelectric properties of the AgXO 2 (X = In, Y) materials with delafossite-type structure, by using the "full-potential linearized augmented plane wave (FP-LAPW)" method. The calculated structural parameters of the title compounds are in excellent agreement with the available theoretical data. We have explored the dynamical stability of the AgXO 2 compounds by investigating the phonon dispersion curves. The optoelectronic characteristics of the studied compounds were accurately described at the level of the "Trans Blaha modified Becke-Johnson (TB-mBJ)" approach to model the exchange-correlation potential. On the other hand, the optical characteristics of the AgInO 2 and AgYO 2 thin films were investigated in the wavelength range 200–750 nm for three different thicknesses: 300, 600 and 1300 nm on a transparent substrate (glass: n glass = 1. 5, k glass = 0). Thermodynamic and thermoelectric properties of the considered compounds were predicted by employing the "quasi-harmonic Debye model" and the Boltzmann transport theory. [ABSTRACT FROM AUTHOR]

• Structural, electronic and elastic properties of Ga 3 Sc intermetallic compound were investigated via DFT. • Phase stability and structure of Ga 3 Sc in L1 2 and D0 22 and D0 23 phases were studied for the first time. • Pressure dependent electronic and bonding characters of Ga 3 Sc polymorphs were studied for the first time. • Various thermo-physical properties were investigated within the quasi-harmonic approximation. • Theoretical results showed good agreement with prior experimental and theoretical findings, where available. In this paper, we present computational results of the structural, mechanical, electronic, elastic, and thermal properties of the binary intermetallic compound Ga 3 Sc by using the full potential linearized augmented plane wave method. The total energy calculations reveal that the cubic L1 2 structure for Ga 3 Sc is more stable than the tetragonal D0 22 and D0 23 structures. The ground-state structural and mechanical properties including the lattice constants (a, c), bulk modulus (B) and its pressure derivative (B′) are estimated by different approximations. The single-crystal elastic constants C ij are calculated. Similarly, the shear modulus (G H), Young's modulus (E), Poisson's ratio (ν), and the elastic anisotropy factor (A) are also derived for polycrystalline Ga 3 Sc using the Voigt-Reuss-Hill approximations. Analysis of the calculated elastic constants C ij , B/G ratios and the Cauchy pressure (C 12 –C 44) shows that these compounds are mechanically stable and brittle in nature. The electronic and bonding properties are discussed from the calculations of band structures, densities of states and electron charge densities. The quasi-harmonic Debye model is used to predict thermodynamic properties of Ga 3 Sc at different temperatures and pressures. [ABSTRACT FROM AUTHOR]

Structural parameters, elastic constants, electronic structure and optical functions of the ternary tetragonal chalcogenides KAlTe 2 and KInTe 2 are predicted via ab initio calculations. The calculated structural parameters and interatomic distances agree very well with the existing experimental results. The computed band structures show that the two studied materials are semiconductors with indirect band-gaps. The computed partial density of states diagrams, charges transfer and distribution of charge density show that the interatomic bonds are mainly of a covalent nature. The calculated elastic constants indicate that the title compounds are mechanically stable and elastically strongly anisotropic. The calculated optical spectra for both explored compounds exhibit a significant optical anisotropy. Both compounds have a low absorption in the visible range compared to the infrared (IR) domain. The refractive index spectrum of KInTe 2 is more anisotropic than that of KAlTe 2. [ABSTRACT FROM AUTHOR]

• Some Physical properties for BeO 1−x A x alloys are investigated. • The calculated ground states properties for BeA compounds compare well with the available data. • Alloying BeO and BeX change the nature of band gap compared to the parent compounds. • The optical and the thermodynamic properties for are investigated for the first time. Special quasi-random structure (SQS) was used to investigate the structural, electronic, and optical characteristics of the binary and ternary beryllium chalcogenide alloys. The computations were performed using the pseudopotential technique. The GGA-WC scheme was applied to study the structural and optical features of these present alloys, while the HSE06 hybrid functional was used to correct the underestimation of the electronic band structure. The optimized lattice constants and bulk modulus demonstrate a non-linear tendency with increasing x concentration. The phase transition may occur for all ternary alloys at x = 0.5 with the orthorhombic assumed crystal system. The ternary alloys of BeO 1− x A x (A = S, Se) at 0.5 ⩽ x ⩽ 1 have an indirect band gap, while BeO 1− x Te x 0.5 ⩽ x ⩽ 1 manifest a metallic demeanor using HSE06 formalism. The optical spectra were computed and discussed in detail. Furthermore, the thermodynamic stability of the studied compounds was examined using the miscibility critical temperature. [ABSTRACT FROM AUTHOR]

DFT based prediction of elastic moduli, energy gaps, and optical parameters of the indirect gap semiconductors of title [ABSTRACT FROM AUTHOR]

We explored the pressure-induced structural phase transitions and elastic properties of AuMTe 2 (M = Ga, In) using the full-potential linearized augmented plane wave method within the framework of density functional theory, applying both generalized gradient and local density approximations. Thermodynamic properties were further assessed through the quasi-harmonic model. We determined the transition pressures for the phase shift from the chalcopyrite structure to the NaCl rock-salt phase in both AuGaTe 2 and AuInTe 2 . Additionally, we calculated and analyzed mechanical properties, such as bulk modulus, shear modulus, Young's modulus, Poisson's ratio, elastic anisotropy, ductility versus brittleness, and hardness for the polycrystalline forms of AuMTe 2 (M = Ga, In). The study also examined how temperature and pressure affect the Debye temperature, heat capacities, thermal expansion, entropy, bulk modulus, Grüneisen parameter, and hardness, utilizing the quasi-harmonic Debye model.

We presented the results of various aspects related to structural, elastic, electronic, dynamic, and magnetic parameters of cubic perovskite CeCrO 3 by means of the full-potential linearized augmented plane wave (FP-LAPW) approach. The calculation of the unit cell volume against the total energy curve confirms that CeCrO 3 exhibits higher energetic stability in the ferromagnetic (FM) order. Calculated structural aspects at equilibrium demonstrate excellent similarity to present information, lending credibility to our results. Moreover, monocrystalline elastic constants have been analyzed numerically. These constants provide insights into several related properties, including elastic anisotropy, mechanical stability, and several polycrystalline elastic aspects. Furthermore, the phonon dispersion curves obtained from our calculations reveal the existence of soft modes, which suggests the potential metastability of CeCrO 3 . Through an analysis of the energy band dispersions, the half-metallic nature of this material is confirmed, such as E g = 3.00 and 3.13 eV for the HM state within generalized gradient approximations Perdew-Burke-Ernzerhof (GGA-PBE) and Tran-Blaha modified Becke-Johnson (TB-mBJ) calculations, respectively, as well as the FM total magnetic moment of 4.000 μB. Partial density of states (PDOS) aided in identifying the electronic states that contribute to the energy bands. Finally, the computed total magnetic moment aligns fit the theoretical findings available in the literature., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

In this work, we have conducted an ab initio computational research of the pressure impact on the structural, elastic, thermodynamic, electronic, and optical properties of Be-based fluoroperovskite XBeF3 (X= K, Rb) compounds by using GGA+ PBEsol functional based on DFT in the CASTEP Package. These compounds' ground state characteristics were examined, including the lattice parameters, coefficient compressibility (B), and its pressure derivative(B'). Structural characterization shows that these compounds keep a cubic crystal structure with the impact of stress till 18 GPa. In addition, we computed elastic constants, Young's modulus (E), shear modulus (G), Poisson's ratio (σ), and the anisotropy factor (A). As the elastic stiffness parameters comply with the Born stability criterion, the examined phases are mechanically stable. The ductility of phases XBeF3 (X= K, Rb) has been assured from the high coefficient compressibility (B) and Pugh's ratio values. Furthermore, we determined the thermodynamic behavior of XBeF3 (X= K, Rb) through the quasi-harmonic Debye model. The electronic band structure and DOS (Density of States) were studied, which provide information on the insulator properties of the two compounds. Also, we studied various optical properties of the materials including: refractive index, optical reflectivity, coefficient of absorption, both real and imaginary parts of dielectric function and lastly the energy loss function. On the basis of these reported studies of these materials, their applications in many modern electronic devices can be predicted., (© 2023 IOP Publishing Ltd.)

In this work, two kinds of competition between different Heusler structure types are considered, one is the competition between XA and L2 1 structures based on the cubic system of full-Heusler alloys, Pd 2 YZ ( Y = Co, Fe, Mn; Z = B, Al, Ga, In, Tl, Si, Ge, Sn, Pb, P, As, Sb). Most alloys prefer the L2 1 structure; that is, Pd atoms tend to occupy the a (0, 0, 0) and c (0.5, 0.5, 0.5) Wyckoff sites, the Y atom is generally located at site b has a preference for site Z has a preference for site d (0.75, 0.75, 0.75), meeting the well known site-preference rule. The difference between these two cubic structures in terms of their magnetic and electronic properties is illustrated further by their phonon dispersion and density-of-states curves. The second type of competition that was subjected to systematic study was the competitive mechanism between the L2 1 tetragonal system. A series of potential tetragonal distortions in cubic full-Heusler alloys (Pd 0 tetragonal system. A series of potential tetragonal distortions in cubic full-Heusler alloys (Pd 2 YZ ) have been predicted in this work. The valley-and-peak structure at, or in the vicinity of, the Fermi level in both spin channels is mainly attributed to the tetragonal ground states according to the density-of-states analysis. Δ E M is defined as the difference between the most stable energy values of the cubic and tetragonal states; the larger the value, the easier the occurrence of tetragonal distortion, and the corresponding tetragonal structure is stable. Compared with the Δ E M values of classic Mn 2 -based tetragonal Heusler alloys, the Δ E M values of most Pd 2 Co Z alloys in this study indicate that they can overcome the energy barriers between cubic and tetragonal states, and possess possible tetragonal transformations. The uniform strain has also been taken into consideration to further investigate the tetragonal distortion of these alloys in detail. This work aims to provide guidance for researchers to further explore and study new magnetic functional tetragonal materials among the full-Heusler alloys.

Magnetic Heusler compounds (MHCs) have recently attracted great attention since these types of material provide novel functionalities in spintronic and magneto-electronic devices. Among the MHCs, some compounds have been predicted to be spin-filter semiconductors [also called magnetic semiconductors (MSs)], spin-gapless semiconductors (SGSs) or half-metals (HMs). In this work, by means of first-principles calculations, it is demonstrated that rare earth-based equiatomic quaternary Heusler (EQH) compounds with the formula M CoV Z ( M = Lu, Y; Z = Si, Ge) are new spin-filter semiconductors with total magnetic moments of 3 µ B . Furthermore, under uniform strain, there are physical transitions from spin-filter semiconductor (MS) → SGS → HM for EQH compounds with the formula LuCoV Z , and from HM → SGS → MS → SGS → HM for EQH compounds with the formula YCoV Z . Remarkably, for YCoV Z EQH compounds there are not only diverse physical transitions, but also different types of spin-gapless feature that can be observed with changing lattice constants. The structural stability of these four EQH compounds is also examined from the points of view of formation energy, cohesive energy and mechanical behaviour. This work is likely to inspire consideration of rare earth-based EQH compounds for application in future spintronic and magneto-electronic devices.