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Magnetic and optical properties of (Mn, Fe)-doped SiC nanosheet (NS) are investigated using first principle calculations based on Density Functional Theory (DFT) within the Full Potential Linearized Augmented Plane Wave (FP-LAPW) method. The Generalized Gradient Approximation (GGA) shows that doping SiC NS by Mn has a half-metal ferromagnetic behavior when one Si atom is replaced by Mn or Fe. We also study the effect of (Mn, Fe) doping on optical properties of SiC NS such as absorption coefficient and optical reflectivity as function of energy. We found that doping SiC NS increases the absorption coefficient, the optical conductivity and the reflectivity in the visible region.

The structural, electronic, elastic and thermodynamic properties of Curium Monopnictides CmX (X = N, P, As, Sb and Bi) are investigated using first-principles calculations based on the density functional theory (DFT) and full potential linearized augmented plane wave (FP-LAPW) method under ambient condition and high pressure. The exchange-correlation term is treated using two approximations spin-polarized local density approximation (LSDA) and spin-polarized generalized gradient approximation generalized (GGA). The structural parameters such as the equilibrium lattice parameters, bulk modulus and the total energies are calculated in two phases: namely NaCl (B1) and CsCl (B2). The obtained results are compared with the previous theoretical and experimental results. A structural phase transition from B1 phase to B2 phase for Curium pnictides has been obtained. The highest transition pressure is 122 GPa for CmN and the lowest one is 10.0 GPa for CmBi compound. The electronic properties show that these materials exhibit half-metallic behavior in both phases. The magnetic moment is found to be around 7.0 $\mu$B. The mechanical properties of CmX (X = N, P, As, Sb and Bi) are predicted from the calculated elastic constants. Our calculated results are in good agreement with the theoretical results in literature. The effect of pressure and temperature on the thermodynamic properties like the cell volume, bulk modulus and the specific heats C${}_{𝜗}$ and C${}_P$, the entropy ${𝒮}$ and the Grüneisen parameter $\gamma$ have been foreseen at expanded pressure and temperature ranges.

The structural, electronic, optical properties and band offsets of Co₂VGa/GaAs(001) interfaces are discussed within the framework of density functional theory (DFT) using the FP-LAPW method, and the exchange-correlation potential is approximated by GGA. All interface structures are stable in the energy point of view, however the V–Ga/As case is found to be more stable than the others. A remarkable potential difference ($\mathrm{\Delta }$V) appeared in all the interfaces, so the Co₂VGa/GaAs(001) interfaces are good candidates for electron injection. In all the cases, there is no full spin polarization at the Fermi level, but high CBO and ${\mathrm{\Phi }}_p$ coefficients make them promising candidates for spin injection in the transport devices. Optical studies confirm the high metallic treatment of these interfaces as the main electron transitions had occurred in the infrared and visible regions. The real parts of the dielectric function in the x-direction indicate the different behaviors of “Co–Co/As and V–Ga/Ga” and “Co–Co/Ga and V–Ga/As” in the infrared area. In addition, the plasmon frequencies had occurred at high UV energies.

In this paper, we explore the structural, electronic, thermoelectric and elastic properties of intermetallic compounds ScTM (TM = Cu, Ag, Au and Pd) using density functional theory. The produced results show high values of Seebeck coefficients and electrical conductivity for these materials. High power factor for these materials at room-temperature shows that these materials may be beneficial for low-temperature thermoelectric devices and alternative energy sources. Furthermore, elastic properties of these compounds are also calculated, which are used to evaluate their mechanical properties. The Cauchy’s pressure and B/G ratio figure out that these compounds are ductile in nature. The calculated results also predict that these compounds are stable against deforming force.

Geometric and electronic structures of W${}_m$Mo${}_n$ (m + n$\le$ 7) clusters have been systematically calculated by density functional theory (DFT) at the generalized gradient approximation (GGA) level for ground-state structures. Geometry optimization shows that clusters are almost bipyramid structures with m + n$>$ 4. E${}_b$ of clusters is mainly dominated by W atoms. And the substitution of atoms between W and Mo in Mo${}_n$ or W${}_n$ (n$\le$ 7) clusters enhances the stability of the original clusters. The calculated IE shows that W${}_{1,3,5}$Mo, W${}_{1,3,5}$Mo₂, W${}_{1,2,3}$Mo₃ and WMo${}_{4,5}$ are relatively more stable in the chemical reaction. In addition, the magnetism of clusters mainly comes from valance d orbitals.

In the present work, first-principles calculations were performed to obtain the structural, electronic and optical properties of lithium niobate crystal using two exchange-correlation functionals (GGA-PBE and TB-mBJ). The calculated structural parameters were very close to the experimental values. TB-mBJ functional was found to be good when compared to LDA and GGA functionals in case of bandgap energy of 3.715 eV of lithium niobate. It was observed that the upper valence and lower conduction bands consist mainly the O-2p and Nb-4$d$ states, respectively. Furthermore, calculations for real and imaginary parts of frequency-dependent dielectric function $𝜀(\omega )$ of lithium niobate crystal were performed using TD-DFT method. The ordinary refractive index n${}_o(\omega )$, extraordinary refractive index n${}_e(\omega )$, its birefringence and absorption peaks in imaginary dielectric function ${𝜀}_2(\omega )$ were also calculated.

Electronic, mechanic and lattice dynamic properties of yttrium-based compounds, X₃Y, where X = Pd, Pt and Rh were investigated using the density functional theory. The electronic band calculations demonstrated that X₃Y compounds are metallic at the cubic crystal structures. The calculated elastic constants using the energy-strain method indicate that the three materials are mechanically stable. The calculated bulk modulus and Young’s modulus values suggest that the Pt₃Y is stiffer than that of the other two. The type of bonding and ductility in the X₃Y compounds were also evaluated based on their B/G ratios, Cauchy pressures (C${}_{12}$–C${}_{44}$) and band structure calculations. These compounds were found to be ductile in nature. The density functional perturbation theory was used to derive full phonon frequencies and total and projected phonon density of states. The computed full phonon spectra for X₃Y compounds show that these compounds in the L1₂ phase are dynamically stable. Debye temperature and specific heat of these compounds were also calculated and evaluated using quasi harmonic approximation.

Half-metallic, optical and thermodynamic phase diagrams of two-dimensional Mn₂ZrZ (Z = Ge, Si) have been calculated by density functional theory (DFT) framework with full-potential linear augmented plane-wave (FP-LAPW) method. The spin-polarized electronic computations show that these layers have metallic behavior with a spin polarization less than 100%. It is observed that with increasing thickness of the layers, both the thermodynamic and energy stabilities increased, and the graphene-like layers of Mn₂ZrGe with a thickness of 7.6955 Å and Mn₂ZrSi with a thickness of 7.551 Å are completely stable thermodynamically. The optical responses of Mn₂ZrZ (Z = Ge, Si) have anisotropy at infrared region versus the optical direction and have high metallic nature in this optical range. The plasmonic frequencies have occurred after the visible edge and the refraction index becomes lower than one after the ultra-violet edge.

We have performed the first-principles density functional theory (DFT) and DFT$+$U calculations on the electronic and optical properties of CaO: Eu${}^{+2}$ (SrO: Eu${}^{+2}$) phosphors compounds. Herein, we have focused on the polarization of the electronic structures, i.e., the energy bandgap and the density of states. All electrons were treated within the most common exchange and correlation functional called generalized gradient approximation plus optimized effective Hubbard parameter U as GGA$+$U. GGA$+$U is a very effective tool for describing the electronic band energy upto considerable accuracy. Hence, we have opted for the arbitrary values of U as 3.0, 4.0, 5.0 and 7.0 eV to treat the strongly correlated electrons for obtaining the matching result with the experimental one. However, GGA$+$U is highly expensive in terms of computation due to interaction of d or f electrons. The result shows that the appearance of Eu-4f states at the valance band maximum of the spin-up causes a substantial impact on the electronic properties of the studied compounds. The value of energy bandgap is smaller in case of spin up as compared to spin down case. In case of majority spin, the energy gap of 2.224 (2.14) eV belongs to the Eu-4f orbitals and governs the CBM. The partial densities of states (PDOS) structure displays a strong hybridization that may be pointed to the formation of covalent bonds. The calculated and the measured values are in good agreement with each other. In the study of optical properties of the compound, the optical spectral structure shows a lossless region and uniaxial anisotropy. The value of uniaxial anisotropy is positive at static limit and its value is negative above this value.

The first-principles study of cubic perovskites SmXO₃ (X = Al and Co) for elastic, mechanical and optical properties is done in the framework of density functional theory (DFT). Optimized structural parameters are obtained first to find mechanical and optical properties of the materials. These obtained structural parameters are in accordance with the published data. The cubic elastic parameters C${}_{11}$, C${}_{12}$ and C${}_{44}$ are then calculated by using generalized gradient approximation (GGA) as an exchange correlation functional in Kohn–Sham equations. Poisson’s ratio, shear modulus, Young’s modulus and anisotropic factor are deduced from these elastic parameters. These compounds are found to be elastically anisotropic and SmAlO₃ is brittle while SmCoO₃ is ductile. Their covalent nature is also discussed by using Poisson’s ratio. In addition, optical properties like absorption coefficient, extinction coefficient, energy loss function, dielectric function, refractive index, reflectivity and optical conductivity are studied. This study predicts that SmAlO₃ and SmCoO₃ are suitable for optoelectronic devices.

Ab initio study has been carried out to investigate the band structure, density of state and optical dielectric function of pure and Nitrogen (N)-doped rutile phase of TiO₂. The band structure obtained with the inclusion of U parameter of 8.5 eV compared favorably with experimental result. Bandgap of N-doped rutile decreases with respect to pure rutile which is traceable to 2p state of the Nitrogen dopant as revealed in partial density of state (PDOS). The optical properties calculated revealed that N-doped rutile has at least one optical peak in the visible light region of the electromagnetic spectrum which suggests it to be a potential material for photovoltaic application than pure rutile. Our results suggest that optical properties of rutile can be adapted by doping with Nitrogen at different concentration which enhances its potential as photocatalyst.

First principles investigations of the electronic, optical and thermoelectric performance of RbZn${}_{1-x}$Ni${}_x$F₃ (x = 0, 0.25, 0.5, 0.75 and 1) alloys are calculated using spin polarized full-potential linear augmented plane wave method, as implemented in Wien2k code. These alloys are found to be stable, ductile and can be formed with ferromagnetic character. RbZn${}_{1-x}$Ni${}_x$F₃ are found to be insulator alloys with bandgap energy of range 7.02–5.14 eV using the modified Becke–Johnson functional. This gap is decreasing with increasing the Ni concentration in the unit cell. The optical parameters are calculated in the energy range upto 35 eV. The calculated static refractive index values are found directly proportional with the higher concentration of Ni atoms in the alloys. The transport coefficients are calculated using BoltzTrap code. The hole assumes the main charge carriers of the present alloys with p-type-doping for RbZnF₃ alloy and n-type-doping for RbZn${}_{1-x}$Ni${}_x$F₃. The calculated optical and transport coefficient values show promising optoelectronic and thermoelectric applications of the studied alloys.

We have examined the magnetic stability; antiferromagnetic (AFM) ordering; electronic and magnetic properties of composition XMn₂Y₂ (X = Ca, Sr; Y = Sb, Bi) using framework of full-potential linearized augmented plane wave (FP-LAPW) method within generalized gradient (PBE-GGA) approximations in AFM phase. We have specified that AFM state is most suitable for these compounds as compared to other configurations at their relaxed lattice parameters. An AFM spin configuration of Mn atoms is shown to be impressive state for these compounds. Based on its electronic properties, these compounds have a metallic nature in Paramagnetic (PM) but in AFM phase it shows different nature from PM phase. From a suitable phase, it has been cleared that both Mn atoms well-adjusted antiferromagnetically.

The mechanical, electronic and thermodynamic properties of Pd₃M (M=Sc, Y) compounds have been investigated using the Full Potential Linearized Augmented Plane Wave (FP-LAPW) formalism. The generalized gradient approximation (GGA) is used to treat the exchange–correlation terms. The calculated formation enthalpies and the cohesive energies reveal that the L1₂ structure is more stable than the D0${}_{24}$ one. The obtained lattice parameters and bulk modulus calculations conform well to the available experimental and theoretical results. The elastic and mechanical properties are analyzed and results show that both compounds are ductile in nature. The Debye temperature and melting temperature are also estimated and are in a good agreement with experimental findings. The total and partial densities of states are determined for L1₂ and D0${}_{24}$ structures. The density of states at the Fermi level, $N$($E_{\mathrm{\text{F}}}$), indicates electronic stability for both compounds. The presence of the pseudo-gap near the Fermi level is suggestive of formation of directional covalent bonding. The number of bonding electrons per atom $n_b$ and the electronic specific heat coefficient $\gamma$ are also determined. The quasi-harmonic Debye model has been used to explore the temperature and pressure effects on the thermodynamic properties for both compounds.

The ab initio calculation is performed to investigate about the structural and the electron transport properties of the experimentally reported (parent) compounds viz., BaFe₂As₂, SrFe₂As₂, CaFe₂As₂ and the novel compounds which are anticipated from our computational work namely BaFe₂Bi₂, SrFe₂Bi₂, CaFe₂Bi₂ with different magnetic order. The space group of the reported compounds is I4/mmm (139) and belong to ThCr₂Si₂ type. The formation energies of the reported compounds are compared in the anti-ferromagnetic (AFM), nonmagnetic (NM) and ferromagnetic (FM) orders. From the comparison, it reveals that the anti-ferro magnetism is the stabled state for the reported compounds. At ambient temperature with constant relaxation time, the resistivity, power factor, Seebeck coefficient and electrical conductivity are computed by using BoltzTraP transport theory code. To explain the superconducting nature of the novel compounds the transition temperature (T${}_C$), electron–phonon coupling factor and Debye temperature are calculated and presented. The mechanical stability of the compounds is examined by using Young’s, bulk and shear modulus, anisotropy constant and Poisson’s ratio which are calculated by using Tetra-elastic code. The Mechanical Temperament of these compounds is analyzed by using Pugh’s ratio. The ELATE tool is used to visualize the elastic properties of these compounds. The thermodynamical stability of the compounds is examined by using Gibbs free energy, vibrational Helmholtz free energy and entropy which are calculated by using Gibbs2 code. All the properties of the theoretically predicted (novel) compounds are analyzed and compared with their parent (experimentally reported) compounds.

The structural, electronic, elastic and thermodynamic properties of ${\mathrm{\text{V}}}_2\mathrm{\text{AX}}$ ($\mathrm{\text{A}}=\mathrm{\text{B}}$, Al, Ga, In and TI; $\mathrm{\text{X}}=\mathrm{\text{C}}$ and N) phase have been systematically investigated by the first principles. The optimized lattice parameters are in good agreement with the experimental values and better than the available theoretical data. We calculated the elastic constants $C_{ij}$ and the total density of states, which verified mechanical stability and electronic structural stability, respectively. The other elastic parameters including bulk modulus, shear modulus, Young’s modulus, Cauchy pressure, shear anisotropy factor, linear compressibility coefficients, Pugh’s ratio, Poissons’s ratio, microhardness parameter and machinability index are calculated and discussed in this work. The results show that the compounds we studied are stable in mechanics and are anisotropic materials; the compressibility along $c$-axis is lower than that along $a$-direction except for ${\mathrm{\text{V}}}_2\mathrm{\text{BX}}$ ($\mathrm{\text{X}}=\mathrm{\text{C}}$ and N); the compounds of ${\mathrm{\text{V}}}_2\mathrm{\text{AC}}$ ($\mathrm{\text{A}}=\mathrm{\text{B}},\mathrm{\text{Al}},\mathrm{\text{Ga}},\mathrm{\text{TI}}$) and ${\mathrm{\text{V}}}_2\mathrm{\text{AN}}$ ($\mathrm{\text{A}}=\mathrm{\text{B}},\mathrm{\text{Al}},\mathrm{\text{Ga}}$) are brittle in nature, and ${\mathrm{\text{V}}}_2\mathrm{\text{InN}}$ and V₂TIN are ductile in nature; the shear modulus $G$ limits the mechanical stability of the materials under consideration; the ability to resist shape change and the stiffness of ${\mathrm{\text{V}}}_2\mathrm{\text{AC}}$ are stronger compared with ${\mathrm{\text{V}}}_2\mathrm{\text{AN}}$ when A takes B, Al, Ga, In, TI, respectively. Finally we have estimated the Vickers hardness which shows that the hardness of the ${\mathrm{\text{V}}}_2\mathrm{\text{AX}}$ ($\mathrm{\text{A}}=\mathrm{\text{B}}$, Al, Ga, In, TI) would decrease when C is replaced by N. At last, we investigated the thermodynamic properties of ${\mathrm{\text{V}}}_2\mathrm{\text{AX}}$ by calculating the phonon dispersion, Debye temperature and minimum thermal conductivity. The results show that all structures are dynamical stable and the compounds of ${\mathrm{\text{V}}}_2\mathrm{\text{BC}}$, ${\mathrm{\text{V}}}_2\mathrm{\text{BN}}$, ${\mathrm{\text{V}}}_2\mathrm{\text{AlC}}$ and ${\mathrm{\text{V}}}_2\mathrm{\text{AlN}}$ are candidates for thermal barrier coating (TBC) materials.

In this work, Mn${}^{2+}/$Eu${}^{3+}$ co-doped Zn₂GeO₄ (Zn₂GeO₄:Mn${}^{2+},{\mathrm{\text{Eu}}}^{3+})$ was prepared by high-temperature solid phase method. Compared with common fluorescent materials Zn₂GeO₄:Mn${}^{2+}$, Zn₂GeO₄:Mn${}^{2+},{\mathrm{\text{Eu}}}^{3+}$ could not only emit strong green fluorescence of 535 nm, but also maintain excellent persistent luminescence performance. Through Density Functional Theory calculation, we obtained the fine band structure of Zn₂GeO₄:Mn${}^{2+},{\mathrm{\text{Eu}}}^{3+}$. The results of the band structure were consistent with the experimental spectral data. On this basis, we proposed a new luminescence mechanism model of Zn₂GeO₄:Mn${}^{2+},{\mathrm{\text{Eu}}}^{3+}$ to explain the phenomena observed in experiment reasonably, though which was not completely consistent with previous works. When Zn₂GeO₄:Mn${}^{2+},{\mathrm{\text{Eu}}}^{3+}$ was excited, electron–hole separation occurred in the valence band (VB), and the electron transitioned to the conduction band (CB) directly. Through CB, the electron was trapped by trap levels (⁷F${}_0{\sim }^7$F₅ of Eu${}^{3+})$ and maintained metastable for a long time. Under the action of thermal stimulation, electron returned to CB from the trap level slowly. The electron was captured again by the ⁴T₂(D) level of Mn${}^{2+}$. Then the electron transitioned down toward VB and recombined with the previous hole and emitted a photon with 535 nm (afterglow). The samples were being irradiated, trap levels accommodated the excited electrons to saturation. More electrons excited into the CB could not be captured by the trap levels any more. They were captured directly by the ⁴T₂(D) and transitioned directly to VB, then emitted green fluorescence.

This work is a part of a series of investigations devoted to the study of the relationship between nonlinear optical properties and pseudosymmetric features of some groups of crystal compounds [A. P. Gazhulina and M. O. Marychev, Cryst. Struct. Theory Appl. 2, 106 (2013). doi.org/10.4236/csta.2013.23015; A. P. Gazhulina and M. O. Marychev, J. Alloys Compd. 623, 413 (2015). doi.org/10.1016/j.jallcom.2014.11.028; A. P. Gazhulina and M. O. Marychev, J. Solid State Chem. 239, 170 (2016). doi.org/10.1016/j.jssc.2016.04.034]. Crystals of the wurtzite ($B$4) structural type (45 crystals) have been considered. In the framework of density functional theory, the structural, electronic, linear and nonlinear optical properties were investigated using the full-potential linearized augment plane wave (FP-LAPW) method. The obtained results are compared to available experimental and computational data. Diagrams “Second-order Nonlinear Susceptibility–Degree of Pseudoinversion” at 1.064 and 0.634 $\mu$m wavelengths were constructed.

Using Monte Carlo Basin-hopping algorithm within the Gupta potential, a systematic investigation has been performed for the best chemical ordering structures of 19-atom trimetallic ${\mathrm{\text{Pd}}}_n{\mathrm{\text{Ag}}}_{(17-n)}{\mathrm{\text{Pt}}}_2$ nanoclusters with double icosahedral geometry. The structures with the lowest energy at Gupta level are then re-optimized by DFT relaxations and the DFT relaxations confirmed the lowest energy structures obtained at the Gupta level indicating the double icosahedron structure is favorable for 19-atom ${\mathrm{\text{Pd}}}_n{\mathrm{\text{Ag}}}_{(17-n)}{\mathrm{\text{Pt}}}_2$ nanoclusters. It was observed that the caloric curves exhibit a smoother transition with structural isomerizations other than a sharp jump behavior.

The Half Heusler alloy (HHA) MnCrP has been studied theoretically for structural, elasto-mechanical and phonon properties. The structure is optimized and the calculated structural parameters are close to the literature. This optimized data is used to estimate three independent second-order cubic elastic constants $C_{11}$, $C_{12}$ and $C_{44}$. The mechanical stability criteria are explored by these constants and further used to estimate the elastic moduli; Young’s, bulk and shear modulus. The mechanical parameters like Poisson’s ratio, Pugh’s ratio, anisotropic factor, Cauchy pressure, shear constant, Lame’s constants, Kleinman parameter are also calculated and discussed. Discussions reveal the ductile nature, ionic behavior, anisotropic nature and mechanical stability of MnCrP. The metallic nature, compressibility, stiffness and interatomic forces of material are also described. Furthermore, the Debye temperature, where the collective vibrations shifts to an independent thermal vibrations, is also calculated. Longitudinal and transverse sound velocities are also obtained to investigate the phonon modes of oscillation. These phonon modes confirm the stability of the alloy as no negative phonon frequencies in the phonon-dispersion curves. These curves are used to estimate the reststrahlen band where light reflects 100% and the suitability of material is checked for Far Infrared (FIR), photographic, optoelectronic devices and sensors.