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Highlights: [•] The available theoretical studies on the antiperovskites SbNCa3 and BiNCa3 were not consistent with the experiments. [•] These compounds are theoretically revisited with LDA, GGA, EV-GGA and mBJ potentials. [•] Both of them are found direct bandgap semiconductors. [•] The bandgaps for both of them is about 1.1eV. [•] Realizing the importance of these compounds in optical devices, optical properties are also discussed. [ABSTRACT FROM AUTHOR]

Highlights: [•] CdS x Se1−x (0⩽ x ⩽1) is theoretically investigated with mBJ. [•] Phase transformation from zinc-blende to wurtzite is observed at 60%-S. [•] The variable band gap nature is direct in the visible region for both structures. [•] The material is optically anisotropic in hexagonal phase. [•] Birefringence is positive at low frequencies and negative at higher frequencies. [ABSTRACT FROM AUTHOR]

In this study, all-inorganic two-dimensional Dion–Jacobson halide perovskites (DJ-HPs) CsMX 2 Y 2 (M = Sb, Bi; and X/Y= I/I, I/Br, Br/Br, I/Cl, Br/Cl, Cl/Cl) have been studied for photovoltaic, photoemission and other potential applications in optoelectronic devices using first principle calculations within the framework of density functional theory (DFT). The ground state crystal symmetry is tetragonal with a P 4/ mmm (No. 123) space group. In these compounds, Cs+ is a spacer cation, which separates the octahedral layers and balances the charge. The corner sharing M-centered (Sb, Bi) [MX 2 Y 4 ]3– unit constructs the 2D [MX 2 Y 2 ] n n– plane, where the X and Y (halogens) atoms occupy the out of plane apical and in-plane bridging sites, respectively. The DJ-HPs with P 4/ mmm crystal symmetry exhibit pseudo-direct band gap semiconducting nature and the spin orbit (SO) effect reduces the band gaps as well as splits the Sb/Bi-p orbital in the bottom of conduction band (CB) and X/Y-p orbital at the top of valence band (VB). Among these DJ-HPs, the band gap energies of CsSbI 2 Cl 2 (0.87 eV), CsSbBr 2 Cl 2 (1.00 eV), CsSbCl 4 (1.40 eV), CsBiI 4 (1.10 eV), CsBiI 2 Br 2 (1.40 eV) and CsBiBr 4 (1.60 eV) lie in a band gap energy range (0.9–1.6 eV) suitable for photovoltaic applications. The M-s (Sb-5s and Bi-6s) and X/Y-p (Cl-3p, Br-4p and I-5p) orbitals are responsible for the electron transition from the valence to conduction band, while the spacer cation (Cs+) has a limited effect on the charge carrier mobility. The effective masses of the charge carriers and exciton binding energies of these materials are suitable for solar cell and optoelectronic applications. From the optical coefficients it is clear that these DJ-HPs have excellent response to the incident photons in the visible and ultraviolet light region. • New Dion–Jacobson two dimensional halide are investigated for optoelectronic applications. • These compounds belongs to tetragonal symmetry having space group P 4/ mmm. • Band gap of these semiconductors are pseudo direct and spin orbit (SO) effect increases from Sb to Bi and Cl to I. • The effective masses of the carriers are increasing linearly with the increasing band gaps. [ABSTRACT FROM AUTHOR]

DFT studies are performed to investigate the structural, mechanical and magneto-electronic properties of the TlTF 3 (T=Fe, Co and Ni) perovskites for the first time using GGA, GGA+U and hybrid density functional theory (HF). Our calculations show that HF give better results than GGA and GGA+U and more consistent with the experiments. The comparison of the lattice constants calculated by HF with experiments shows a maximum underestimation less than 0.2%. The chemical bonding between different ions in these compounds is explained on the bases of electronic clouds, which reveals that in TlFeF 3 , Fe has more ionic character with F than the rest. The mechanical properties explain the hardness of these compounds and show that TlFeF 3 is more ductile. Spin-dependent electronic band profiles show that TlFeF 3 and TlCoF 3 are metallic, whereas TlNiF 3 is pseudo direct wide bandgap semiconductor. The stable magnetic phase optimizations and the calculated magnetic susceptibility confirm that TlFeF 3 and TlNiF 3 are ferromagnetic whereas TlCoF 3 is anti-ferromagnetic material. [ABSTRACT FROM AUTHOR]

Ferromagnetic metallic inverse-perovskite (Eu 3 O)In is studied using hybrid functional theory (HF) in the frame work DFT. The calculated structural parameters and geometries of the material are calculated by different exchange correlation potentials and found that HF results are closed to the experiments. Electronic charge density explains the bond nature and polarization. The spin polarized electronic band profiles and density of states reveal the metallic nature of the compound. The Eu f-state splitting show that the valance bands are dominated mainly by f-[a 2 ], f-[x(T 1 )], f-[y(T 1 )] and f-[z(T 1 )] states. The ground state magnetic phase of the compound is optimized. The optimum energy and magnetic susceptibility confirm the ferromagnetic nature of the compound. On the basis of different properties presented it is predicted that this compound is magnetoresistive material. [ABSTRACT FROM AUTHOR]

Abstract: The all electrons full potential linearized augmented plane waves (FP-LAPW) method with GGA+U is used to study SrTbO3 perovskite in cubic and orthorhombic phases. The structural parameters and ground state magnetic properties are found consistent with the experimental results. The electronic band structures and density of states demonstrate that SrTbO3 is a wide band gap semiconductor in both phases. The magnetic studies of the material show that the nature of the compound is G-type anti-ferromagnetic. The calculated magnetic moment of Tb+4 is found consistent with the experiments. Furthermore, the optical properties demonstrate that the optical gap of the material is 1.8eV, which lies in the visible region of the electromagnetic spectrum and hence the compound can be used in optoelectronic devices. [Copyright &y& Elsevier]

Abstract: Structural and electronic properties of the cubic perovskite ZnTiO3 and spinel Zn2TiO4 are theoretically studied by the modified Becke–Johnson (mBJ) potential within the framework of density functional theory (DFT). The calculated lattice constants are found to be consistent with the experimental results. The electronic band structures of both the materials reveal that ZnTiO3 is an indirect band gap while Zn2TiO4 is a direct band gap semiconductor. The calculated fundamental band gaps of these compounds are 2.7eV and 3.18eV, which are consistent with the experimental band gaps of 2.9eV and 3.1eV, respectively. Zn2TiO4 is a wide and direct band gap compound and hence is an attractive material for optoelectronic applications, especially in near ultraviolet (UV) optoelectronics. Keeping in view the importance of Zn2TiO4 in low frequency UV devices its optical properties like dielectric functions, refractive index, reflectivity and energy loss function are also evaluated and discussed in detail. [Copyright &y& Elsevier]

Abstract: Spin polarization effects on electronic properties of pure LaCoO3 and doped compounds (La0.5Y0.5CoO3, LaCo0.5Mn0.5O3) in the rhombohedral phase have been studied. We have employed the full potential linearized augmented plane wave (FP-LAPW) method with the generalized gradient approximation (GGA+U) under density functional theory (DFT). The calculated band structures along with total as well as partial densities of states reveal that Y and Mn impurities have a significant effect on the structural and electronic properties of LaCoO3. It is found that Mn alters insulating behavior of this compound to the half metallic for spin up state. Obtained results show that the magnetic moment for the Co-3d state is near 3.12μ B in LaCoO3 compound which increases and decreases with addition of Y and Mn dopants respectively. [Copyright &y& Elsevier]

Osmium based perovskites AOsO 3 (A=Ca, Sr and Ba) have been studied theoretically using density functional theory approach. These studies show that CaOsO 3 and SrOsO 3 are orthorhombic and BaOsO 3 is cubic and are consistent with the experiments. The electronic band structures demonstrate that these compounds are metals. The magnetic studies verify the experimental observations at low temperature, where the spin effects are canceled by the orbitals. The stable magnetic phase optimizations and magnetic susceptibilities calculations by the post-DFT treatment confirm that CaOsO 3 and SrOsO 3 are weak ferromagnetic whereas BaOsO 3 is a paramagnetic material. The directional magnetic study shows that these compounds are magnetically anisotropic, and reveals that the easy magnetization axis is [001] direction. [ABSTRACT FROM AUTHOR]

The electronic properties of complex binary skutterudites, MX 3 (M = Co, Rh, Ir; X = P, As, Sb) are explored, using various density functional theory (DFT) based theoretical approaches including Green's Function (GW) as well as regular and non-regular Tran Blaha modified Becke Jhonson (TB-mBJ) methods. The wide range of calculated bandgap values for each compound of this skutterudites family confirm that they are theoretically as challenging as their experimental studies. The computationally expensive GW method, which is generally assume to be efficient in the reproduction of the experimental bandgaps, is also not very successful in the calculation of bandgaps. In this article, the issue of the theoretical bandgaps of these compounds is resolved by reproducing the accurate experimental bandgaps, using the recently developed non-regular TB-mBJ approach, based on DFT. The effectiveness of this technique is due to the fact that a large volume of the binary skutterudite crystal is empty and hence quite large proportion of electrons lie outside of the atomic spheres, where unlike LDA and GGA which are poor in the treatment of these electrons, this technique properly treats these electrons and hence reproduces the clear electronic picture of these compounds. [ABSTRACT FROM AUTHOR]

Highlights: [•] Anti-perovskites NiNMn3 and ZnNMn3 are theoretically investigated. [•] The electronic band structure reveals that both compounds are metals. [•] The optimized ground state magnetic phases of both compounds are anti-ferromagnetic. [•] The magnetic properties show that they can be used in spin based devices. [Copyright &y& Elsevier]

Effect of spin orbit coupling (SOC) on the physical properties of perovskites A 3 SnO (A = Ca, Sr and Ba) have been studied in the domain of density functional theory (DFT). It is found that SOC effect has great influence on the electronic band structures, optical and thermoelectric properties of these perovskites. Dirac cones are observed in the band structures and SOC opens the gap between valence and conduction bands. These compounds have narrow direct band gaps with values 0.27, 0.13 and 0.1 eV respectively. Mechanical properties show that these compounds are elastically stable, anisotropic and ductile. Optical properties show that these compounds are optically active in the infrared region of the electromagnetic spectrum. Thermal conductivity, heat capacity, Seebeck coefficient, Power factor and Figure of merit show that these perovskites could be used in thermoelectric generators. • Spin orbit coupling effect has great influence on the electronic band structure, optical and thermoelectric properties of these perovskites. • Dirac cone are observed by GGA and GGA + mBJ whereas GGA + SOC reveal narrow direct bandgaps semiconducting nature of these compounds. • These compounds are elastically stable, anisotropic and ductile. • These compounds are optically active in infrared region of electromagnetic spectrum. • Thermoelectric properties explore that these perovskites could be used as efficient thermoelectric materials. [ABSTRACT FROM AUTHOR]

Electronic band structure, spontaneous polarization, hyperfine fields and electric field gradients (EFG) of the desirable multiferroic BiFeO 3 (BFO) are explored in R3c space group, using density functional theory. Improved TB-mBJ approach resolves the long-standing inconsistency between the theoretical and experimental band gap nature and value of BFO. In this study the calculated direct band gap is 2.84 eV, which was reported indirect band structures in other theoretical studies. The ferroelectric spontaneous polarization 88 μC/cm2 by PBE-GGA and 81 μC/cm2 by TB-mBJ were obtained using the Berry phase approach. Furthermore, the hyperfine interaction and EFG of the compound are also investigated. Image 1 • Bismuth ferrite (BiFeO 3) is attractive ferroelectric material. • The long-standing controversy in its experimental and theoretical band-gap is resolved. • The hyperfine fields and electric field gradients are calculated for the first time. • The spontaneous polarization of the compound is also explored. [ABSTRACT FROM AUTHOR]

Mg-rich intermetallic NdNiMg 5 in orthorhombic phase with space group Cmcm (No. 63) has been studied theoretically using hybrid functional (HF–B3PW91) within the frame work of density functional theory (DFT). The calculated structural parameters and geometries are found in good agreement with the experiments. The electronic properties of the material reveal the metallic nature. Nd 4f-states splitting show that A 2 , y[t 1 ] and z[t 1 ] contributed in the valence band; x[t 1 ], ksi[t 2 ] and eta[t 2 ] in conduction band; where zeta[t 1 ] state completely lay at the Fermi level make the compound metallic. The electrical properties show that the material has significant conductivity above the room temperature. The stable magnetic phase of the compound is optimized which show that the material is stable in G-type antiferromagnetic (AFM) phase and Nd–Ni direct magnetic exchange interactions are involved. The calculated effective magnetic moments of Nd is 3.70 μ B per unit cell. The post-DFT calculations also confirm the AFM phase of the compound with Neel temperature (T N) = 25 K and Curie-Weiss constant (θ) = −23 K. Based on the above physical properties it is expected that this intermetallic could be used in spin valve and magnetic memory devices. • Mg-rich intermetallic NdNiMg 5 has been investigated theoretically using hybrid density functional theory. • The electronic properties of the material reveal the metallic nature. • The electrical properties show that the material has significant conductivity above the room temperature. • Stable magnetic phase of the compound is G-type anti-ferromagnetic phase. • The post-DFT calculations also confirm the AFM phase of the compound. [ABSTRACT FROM AUTHOR]

• Electronic and optical properties. • Effects of chemical bond strength and electronegativity difference on electronic properties. • Accuracy of improved TB-mBJ exchange potential. • Improved TB-mBJ approach results compared with experimental. The recently developed improved Tran and Blaha modified Becke-Johnson exchange potential (TB-mBJ) approach within the framework of DFT is used to calculate band gaps and optical properties of cubic perovskites ABO 3 (A = Ca, Sr, Ba and B = Ti, Zr, Hf). The bonding nature and electronegativity difference between B-cation and O atoms are considerably influencing the electronic band gaps of these compounds. Improved TB-mBJ treats the electronic density appropriately between them, producing accurate band gaps. The optical response shows wide range of light absorption, from visible to ultraviolet, in these compounds expecting their possible applications in various optoelectronic devices. [ABSTRACT FROM AUTHOR]