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The electronic and the magnetic properties of the double perovskite S r 2 C r W O 6 are studied by using ab-initio density functional theory (DFT) calculations with Generalized Gradient Approximation (GGA) and Monte Carlo simulation within the framework the Ising model. This compound is formed by two magnetic cubic sublattices, one occupied by Chromium C r 3 + with spin (S = 3 / 2) and the other occupied by Tungsten W 5 + with spin (σ = 1 / 2). The density of states (DOS) and the band structure of the compound are investigated. The results show the half metallic behavior of S r 2 C r W O 6 with a total magnetic moment equal to 2 μ B . The degeneracy removed from the orbital d of the Chromium by the octahedral crystal field was discussed. The exchange couplings C r − C r and W − W are ferromagnetic, while the super exchange coupling C r − O − W is antiferromagnetic. Concerning the Monte carlo study, it is seen that the system presents interesting phenomena. In particular, the compensation behavior, the first order transition and multiple hysteresis loops have been obtained. • The electronic and the magnetic properties of the double perovskite Sr 2 CrWO 6 are studied by using DFT and MCS. • The results show the half metallic behavior of Sr 2 CrWO 6 with a total magnetic moment equal to 2μ B. • The compensation behavior, the first order transition and multiple hysteresis loops have been obtained. [ABSTRACT FROM AUTHOR]

The conception and modeling of a photovoltaic cell are done by combining the density functional theory (DFT) and solar cell capacitance simulator (SCAPS). The search for new lead-free halide semiconductor perovskite materials with an appropriate band gap, which can be used as good absorbers of solar radiation in the studied photovoltaic cell, is realized by substituting a percentage of sodium (Na) with potassium (K) and sulphur (S) in the double perovskite Cs 2 NaCrCl 6. The study also focuses on the choice of the best materials for the electron transport layer (ETL) and the hole transport one (HTL) as well as the thickness of the perovskite semiconductor materials Cs 2 Na 1− x X x CrCl 6 (X = S and K). The results reveal that Cu 2 O and WS 2 are suitable materials for HTL and ETL layers, respectively. The optimal thickness of the perovskite semiconductor is equal to 2 μm. Under optimized conditions, the photovoltaic device power conversion efficiency (η) equals 15.01 % and 20.01 % by using Cs 2 Na 0.5 K 0.5 CrCl 6 with E g = 1.8 eV and Cs 2 NaCrCl 6 with E g = 1.6 eV as active layer, respectively. Therefore, the obtained photovoltaic cell model is (Cu 2 O / Cs 2 NaCrCl 6 / WS 2 /FTO), with an efficiency of η = 20.01 %. • New semiconductor perovskite Cs 2 Na 1− x X x CrCl 6 (X = S and K) with appropriate band gap have been found. • Studies of ETL, HTL and semiconductor perovskite thickness have been done. • The efficiency of designed photovoltaic cell (Cu 2 O ∕ Cs 2 NaCrCl 6 ∕ WS 2 ∕FTO) is η = 20.01 %. • Conception and modeling of photovoltaic cell is done by combining DFT and SCAPS. [ABSTRACT FROM AUTHOR]

[Display omitted] • Bi 2 NiCrO 6 is synthesized by the sol–gel method. • Bi 2 NiCrO 6 shows a cubic structure with an Fm3m space group. • Bi 2 NiCrO 6 is a metallic and ferromagnetic material (μ=1.17μB). • Bi 2 NiCrO 6 is a good candidate for spintronic application. In this work, the experimental and theoretical studies of Bi 2 NiCrO 6 double perovskite material have been performed. The synthesis of Bi 2 NiCrO 6 is made by sol–gel method. The X-ray diffraction (XRD) characterisation of the material reveals that the double perovskite adopts a cubic structure (a = 7.75 Å) with Fm3m space group. Based on the Density Functional Theory (DFT) with spin polarized calculations, the electronic and magnetic properties have been investigated. From the total electronic density of states and the electronic band structure analysis, it is found that Bi 2 NiCrO 6 exhibits a metallic behavior. It is also found that the studied compound is ferromagnetic material with a total magnetic moment 1.17 μ B . The results show that Bi 2 NiCrO 6 material is a good candidate for using in devices that requires multifunctional operations including spintronic. [ABSTRACT FROM AUTHOR]

[Display omitted] • DFT has been used to study the optic and electronic properties of Cs 2 AgBiX 6 (X = I ; Br ; Cl and F). • The studied compounds exhibit a semiconductor behavior. • The fluorine based perovskite is the least absorbent. • Bromine and Chlorine based perovskites are very interesting for the photovoltaic and optoelectronic. Lead free halide double perovskites are widely studied for their semiconducting behavior which allows them to be used as absorbing materials in solar cells and optoelectronic applications. In this paper, in order to look for perovskite materials with appropriate absorption and band gap, our aim is to study the electronic and optical properties of Cs 2 AgBiX 6 (X = I , Br , Cl and F) by using the density functional theory (DFT) with generalized gradient approximation (GGA). The found results show that the investigated halide compounds present a semiconductor features which absorb in a long wavelength range. Furthermore, iodine based halide perovskite exhibits a negative values of the dielectric function real part which correspond to a high photon reflection, besides the fluorine one is the least absorbent material. From the obtained results, our work confirm that, bromine and chlorine based double perovskites are very interesting for the photovoltaic and optoelectronic applications. [ABSTRACT FROM AUTHOR]

Anti-perovskite nitride material F e 3 A l N is studied by using the density functional theory with generalized gradient approximation (GGA+U) approaches and the Monte Carlo simulation in the framework of the Ising model. The parameter of the unit cell has been optimized, the electronic band structure, the electronic density of states and the magnetic moments of the compound are discussed. Based on the energy calculations, the exchange interactions and the magnetic anisotropy are calculated in order to perform the Monte Carlo simulation. Therefore the obtained Curie temperature T c =780 (K) of the compound is in agreement with the experimental one T c =770 (K). The magnetic and magnetocaloric properties are also investigated, the maximum entropy change and the RCP values are 3.355 J/Kg.K and 638 J/Kg for h=5T, respectively. Based on the hysteresis loops, the energy product BH was calculated. The obtained B H m a x is equal to 1.26 (MGOe) above the ambient temperature. These results show that the F e 3 A l N compound can be a good candidate for both information storage applications and magnetic refrigeration. • The magnetocaloric effect, electronic and magnetic properties of AlFe3N have been investigated. • Exchange coupling and magnetic anisotropy have been calculated. • Magnetic energy product of AlFe3N has been discussed. • Based on its relative cooling power, AlFe3N is a good candidate for the magnetic refrigeration. • Based on the magnetic energy product, AlFe3N is a hard magnet material. [ABSTRACT FROM AUTHOR]

The double perovskite Ba 2 FeMnO 6 is studied by using density functional theory calculations and Monte Carlo simulation within the framework of the Ising model. Based on the minimum energy, the structure was optimized and the stable configuration of spins in Ba 2 FeMnO 6 double perovskite was determined. The magnetic moments, the band structure and the electronic density of states (DOS) were analyzed in details. The oxide Ba 2 FeMnO 6 exhibits a half-metallic behavior with a band gap close to the value 0.3 (eV). The stable spin configuration is considered for the Monte Carlo simulation. A first order transition and a compensation behavior have been found. • Electronic and magnetic properties of Ba 2 FeMnO 6 are studied by DFT and MCS. • Stable configuration of spins in Ba 2 FeMnO 6 was determined. • Ba 2 FeMnO 6 exhibits a half metallic behavior and a magnetic moment μ = 4. 406 μ B . • Compensation behavior and first order transition have been found. [ABSTRACT FROM AUTHOR]