Showing papers by "Rabah Khenata published in 2023"

Investigation of the structural, mechanical, optoelectronic and, thermoelectric characteristics of cubic GeTiO3: An ab initio study

Abstract: The structural, mechanical, optical, and thermoelectric properties of the cubic perovskite GeTiO3 is investigated using the first-principle method. The full potential linearized augmented plane wave (FP-LAPW) approach is used to solve the Kohn–Sham equations. The local density approximation (LDA), generalized gradient approximation (GGA), and modified Becke-Johnson (mBJ) exchange potentials are used for exchange-correlation effects. The computed lattice constant is in accordance with the experimental results. The band structure calculations reveal that GeTiO3 has an indirect energy band gap (Γ-X) of 2.517 eV. Optical spectra computations such as the real and imaginary components of the dielectric function, reflectivity, and refractive index are performed within the region of 0–10 eV. We considered the maximum transition and absorption coefficients to be 5.8 (2.2 eV), and 4.8 (3.1 eV) respectively. Finally, using Boltzmann transport theory the Seebeck coefficient, electrical, thermal conductivity, and Power factor (PF) of the considered compound is evaluated. We analyzed the maximum PF of approximately 9 × 1011 W/K2ms and 15.9 × 1011 W/K2ms at 1200 K against temperature and chemical potential respectively. The high mobility of carriers improves the Seebeck coefficient, power factor, and electrical conductivity of GeTiO3 compound. Our findings will serve as theoretical guidelines for future experimental and industrial GeTiO3 applications.

Theoretical insight on the electronic band structure, mechanical, vibrational and thermodynamic characteristic of antiperovskitesRE3InN (RE=Y and La)

Abstract: The purpose of the current work is to examine the structural, elastic, phonon, and thermodynamic features of antiperovskites RE3InN (RE = Y and La) compounds using the Full potential augmented plane wave method (FP-LAPW) within the framework of density functional theory (DFT). The generalized gradient approximation of Perdew-Burke and Ernzerhof (GGA-PBE) exchange correlation have been considered to optimize the lattice parameters. The elastic properties of the investigated antiperovskite RE3InN (RE = Y and La) compounds has been studied in terms of Young, shear, bulk modulus, Poisson ratio, Debye temperature etc. The Debye temperature for RE3InN (RE = Y and La) compounds are found to be 575 K, 450 K, respectively. The compound La3InN is ductile while Y3InN compound is brittle in nature as evidenced from Cauchy pressure, Pugh ratio etc. La3InN compound is mechanically stable according to elastic property analysis. The electronic properties analysis suggests that the studiedcompounds aremetallic that arises from Y/La-4d/5d states. Additionally, we computed the thermodynamic variables, such as the bulk modulus B, relative volume, heat capacity, thermal expansion, and relative Debye temperature at a range of temperatures (0–1200 K) and pressures (0–40 GPa). The results that have been revealed should be helpful for future antiperovskite synthesis as well as for expanding our understanding of this promising class of antiperovskite-type materials.

A unified DFT exploration on transport and thermodynamic properties of L21 structure of Rh2XZn (X = Mn, Fe) ferromagnets

Abstract: • L2 1 structure is stable structure for Rh 2 XZn (X = Mn, Fe). • Rh 2 XZn (X = Mn, Fe) are ferromagnetic in nature with 3.12 & 4.6 µ B , magnetic moments. • Low values of thermal conductivity which is accountable for figure of merit. • Predicted ZT for energy based applications. • High values of Debye temperature for the considered materials. Rh 2 XZn (X = Mn, Zn), full-Heusler compounds have been investigated with respect to their transport and thermodynamic properties using the first-principles approach. The full potential linearized augmented plane wave method with different exchange potentials is used to find the structural stability within considered L2 1 and XA structures. Moreover, Rh 2 XZn (X = Fe, Zn) are found to be ferromagnetic with magnetic moments of ∼3 and ∼4µ B , which are compatible with the Pauling-Slater rule. To further seek the application of the material in the transport phenomena, figure of merit has been estimated by using Boltzmann theory. Our calculations lead to a 0.15 value of figure of merit at 1200 K for Rh 2 FeZn. Furthermore, the thermodynamic stability has been examined by considering various parameters within 0 to 1200 K temperature range. One of the novelties lies within the high value of Debye temperature that surmised the materials to be used as hard materials.

Structural, Elastic, Electronic, and Magnetic Properties of Full-Heusler Alloys Sc2TiAl and Sc2TiSi Using the FP-LAPW Method

Abstract: In this article, the structural, elastic, electronic, and magnetic characteristics of both regular and inverse Heusler alloys, Sc2TiAl and Sc2TiSi, were investigated using a full-potential, linearized augmented plane-wave (FP-LAPW) method, within the density functional theory. The optimized structural parameters were determined from the minimization of the total energy versus the volume of the unit cell. The band structure and DOS calculations were performed within the generalized gradient approximation (GGA) and modified Becke–Johnson approaches (mBJ-GGA), employed in the Wien2K code. The density of states (DOS) and band structure (BS) indicate the metallic nature of the regular structure of the two compounds. The total spin magnetic moments for the two compounds were consistent with the previous theoretical results. We calculated the elastic properties: bulk moduli, B, Poisson’s ratio, ν, shear modulus, S, Young’s modulus (Y), and the B/s ratio. Additionally, we used Blackman’s diagram and Every’s diagram to compare the elastic properties of the studied compounds, whereas Pugh’s and Poisson’s ratios were used in the analysis of the relationship between interatomic bonding type and physical properties. Mechanically, we found that the regular and inverse full-Heusler compounds Sc2TiAl and Sc2TiSi were stable. The results agree with previous studies, providing a road map for possible uses in electronic devices.

Insight into the structural, electronic, optical, and elastic properties of niobium carbide

Abstract: ABSTRACT The structural parameters, electronic, optical, and elastic properties of Niobium Carbide (NbC) compound within four different structures: rock-salt (RS), wurtzite (WZ), cesium chloride (CsCl), and Nickel Arsenide (NiAs) are examined using the Full-Potential Linearized-Augmented Plane Wave (FP-LAPW). The exchange–correlation potential (VXC) has been treated by Perdew, Burke, and Ernzerhof's generalized gradient approximation (PBE-GGA) when structural properties, transition pressure, and elastic properties are estimated. For electronic properties, in addition to (PBE-GGA), the modified Becke–Johnson (mBJ-GGA) was used for increased accuracy. Present results show that the RS of NbC is the most stable among the four examined structures with the lowest equilibrium energy. The calculated lattice constants are in good agreement with the former calculations. The elasticity and the formation energy calculations show that NbC is stable within the four studied structures. The electronic band structure calculations of NbC show that it has a metallic nature in the four considered structures.

Structural, electronic, magnetic, and optical investigations of sodium chalcogenides: First-principles calculations

Abstract: The electronic, magnetic, and optical properties of NaS and NaSe compounds have been studied by using first-principles calculations based on density-functional theory and full-potential linearized augmented plane-wave method. The Perdew–Burke–Ernzerhof generalized gradient approximation (PBE-GGA) and modified Becke–Johnson (mBJ-GGA) have been used to deal with the exchange-correlation potential. The PBE-GGA and mBJ-GGA electronic calculation of the spin-up configuration shows an insulating behavior, while the spin-down shows a metallic behavior. In addition, both PBE-GGA and mBJ-GGA agree that the total magnetic moment per unit cell for these compounds is 1 μB. From optical calculations, we see that ε1(0) value in the spin-up channel is positive, which shows an insulating character, while it has a large negative value for the spin-down configuration, which shows a metallic character. The NaS and NaSe refractive index n( ω) indicates a metallic demeanor as the real and imaginary parts of the dielectric constant.

Mechanical Stability, Electronic, and Magnetic Properties of XZrAs (X = Cr, Mn, V) Half-Heusler Compounds

Abstract: The structural, half-metallic, and elastic characteristics of XZrAs (X = Cr, Mn, and V) half-Heusler compounds were theoretically calculated using the WIEN2k code. For the term of the potential exchange and correlation (XC), we calculated structural, electronic, and magnetic properties using the generalized gradient approximation (GGA). The type 1 arrangement in ferromagnetic (FM) phases is more energetically stable than other type arrangements in all compounds. The spin-up electrons of both XZrAs (X = Cr, Mn) half-Heusler compounds in the type III structure are semiconducting with energy gaps, whereas the spin-dn electrons are metallic. Research has also been done on the VZrAs compound, which exhibits metallic characteristics in both type I and type III structures. XZrAs (X = Cr, Mn, and V) half-Heusler compounds are elastically stable and ductile, according to calculated Cij elastic constants. Finally, at equilibrium lattice constants a = 6.1196 A° for MnZrAs and 6.142 A° for CrZrAs, real half-metal ferromagnetic materials (HMF) were produced from XZrAs (X = Cr, Mn) half-Heusler compounds within 3 µB and 2µB, respectively.

Structural, electronic, and elastic properties of RbI using the FP-LAPW method

Abstract: The structural, mechanical, and electronic properties of rubidium iodide (RbI) have been extensively investigated utilizing the generalized gradient approximation (GGA) and the full-potential linearized augmented plane wave (FP-LAPW) approach. The potential was roughly calculated using a modified Becke–Johnson (mBJ) approximation, which increased the precision of the electronic properties. In this study, RbI is analyzed in a wide range of crystal structures, including topologies like rock salt (RS), CsCl, zinc blende (ZB), NiAs, and wurtzite (WZ), among others. Our research shows a strong relationship between the material’s physical properties and the conclusions drawn from both theoretical and experimental studies. Significantly, our results show that the RS form corresponds to RbI’s ground state. All the aforementioned topologies display wide-bandgap semiconductor capabilities, according to further examination of their electronic band structures. Notwithstanding these findings, it was discovered that RbI has a poor fracture resistance due to its low bulk modulus. Born’s stability analysis has shown that RbI is stable in the RS, CsCl, ZB, NiAs, and WZ structures. All RbI structures were discovered to have ionic bonding and to be ductile, and every stabilized system displayed anisotropic stability. Using the Cauchy pressure and Poisson’s ratio, the stiffness of the systems was evaluated, with the RS structure proving to be the stiffest. Overall, the findings illuminate the physical properties of RbI, providing valuable insights that could facilitate the creation and refinement of novel materials possessing desirable characteristics.