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In this paper, the thermo-electric, phonon, electronic, and optical properties of the C3N monolayer have been investigated using the Wien2K computational code based on first principles calculations in the framework of the density functional theory. The study of electronic properties shows the behavior of non-magnetic semiconductors with an indirect gap with a value of 0.5 electron volts for this two-dimensional structure. Also, optical properties such as dielectric function, reflection, energy loss function, absorption coefficient, and optical conductivity are calculated. C3N monolayer is optically anisotropic in z and x direction, which according to the refractive index diagram leads to birefringence, which is a key parameter for this compound's linear optical performance. The results provide a fundamental understanding of the design of composite structures used in nanodevices based on two-dimensional advanced materials. The linear response approach along the symmetric points calculates the phonon dispersion diagram. The results indicate the absence of negative modes in the phonon spectrum, indicating that the structure is dynamically stable. Investigating the thermoelectric properties of the C3N monolayer using the semi-classical Boltzmann theory shows that this monolayer has a value coefficient (ZT) close to one at room temperature and temperatures lower than room temperature. As a result, it can be proposed as a candidate for thermoelectric applications.

In this study, the optical and electronic properties of bulk and nano-layer of zinc selenide (ZnSe) and zinc sulfide (ZnS) are investigated. The calculations for solving the many-body Schrodinger equations are performed in the framework of density functional theory using the WIEN2K computational package. The Engel-Vosko and gradient generalized approximation (GGA) treat the exchange-correlation potential. To investigate the electronic and optical properties of zinc selenide and zinc sulfide nano layers, the electronic band structure and the real and imaginary parts of complex dielectric function for the bulk and nano-layer with different thicknesses are calculated and compared. The results of electronic band structures show that the energy band gap of zinc selenide and zinc sulfide nano-layers with various thicknesses decreases to zero and are metal. In contrast, the bulk of zinc selenide and zinc sulfide compounds are semiconductors. The results also show that for each compounds the static dielectric function for the perpendicular and parallel direction to the nano-layer surface is different from the bulk static dielectric function. Comparison between the real parts of complex dielectric function for the bulk and nano-layer shows that absorption of electromagnetic radiation for the ZnSe and ZnS nano-layer in comparison to corresponding bulk results occur in lower energies.

Context and results : In this paper, the crystal structure, electronic, optical, and mechanical properties of SrVO3 have been systematically studied by first-principles calculation. The results show that the calculated lattice parameters are in good agreement with the experimental values of X-ray diffraction. The density of states is described in detail in this paper. By analyzing the crystal structure and electronic properties of SrVO3, the magnetic properties of SrVO3 are obtained from the one unpaired electrons of V and the exchange interaction between two V ions. At the same time, a detailed analysis of the optical properties of SrVO3 was conducted, and it was found that it is transparent in the visible light range. Finally, the mechanical properties of SrVO3 are calculated, which can provide some references for future research. Computational method: In this paper, a first-principles method based on density functional theory (DFT) is reported for PBE-GGA analysis using the plane wave-pseudo potential method in a quantum concentrate packet, U value of 7 eV to V-d and a U value of 2 eV to O-p, Grimme correction by DFT-D method. The k points in the Brillouin region are set to 4 × 4 × 4. The energy convergence criterion for self-consistent field calculation is set at 5.0 × 10−6 eV/atom, and the cutoff energy is 1170 eV. In this paper, the force acting on each atom is not more than 0.01 eV/Å, the maximum stress is not more than 0.02GPa, and the maximum atomic displacement is 5 × 10−4 Å. [ABSTRACT FROM AUTHOR]

Context and results : In this paper, the crystal structure, electronic, optical, and mechanical properties of SrVO3 have been systematically studied by first-principles calculation. The results show that the calculated lattice parameters are in good agreement with the experimental values of X-ray diffraction. The density of states is described in detail in this paper. By analyzing the crystal structure and electronic properties of SrVO3, the magnetic properties of SrVO3 are obtained from the one unpaired electrons of V and the exchange interaction between two V ions. At the same time, a detailed analysis of the optical properties of SrVO3 was conducted, and it was found that it is transparent in the visible light range. Finally, the mechanical properties of SrVO3 are calculated, which can provide some references for future research. Computational method: In this paper, a first-principles method based on density functional theory (DFT) is reported for PBE-GGA analysis using the plane wave-pseudo potential method in a quantum concentrate packet, U value of 7 eV to V-d and a U value of 2 eV to O-p, Grimme correction by DFT-D method. The k points in the Brillouin region are set to 4 × 4 × 4. The energy convergence criterion for self-consistent field calculation is set at 5.0 × 10−6 eV/atom, and the cutoff energy is 1170 eV. In this paper, the force acting on each atom is not more than 0.01 eV/Å, the maximum stress is not more than 0.02GPa, and the maximum atomic displacement is 5 × 10−4 Å. [ABSTRACT FROM AUTHOR]

Context: In this paper, the optimum coverage of 4.44% and the optimum adsorption sites were determined for the Be3N2 adsorption system of O atoms at different coverages based on density functional theory. The electronic and optical properties of the model were investigated by applying bending deformation to the model at these coverage and adsorption sites. Adsorption of O atoms disrupts the geometrical symmetry of Be3N2, resulting in orbital rehybridization and lowering its band gap. Bending deformation causes the band gap of the adsorbed O atom structure of Be3N2 to first increase and then decrease, resulting in the modulation of its band gap. With increasing bending deformation, the adsorbed system is redshifts, and the degree of redshift increases with increasing bending deformation. Methods: All calculations in this paper were performed using the first-principles-based CASTEP module of Materials Studio (MS). The generalized gradient approximation (GGA) plane-wave pseudopotential method and the Perdew-Burke-Ernzerhof (PBE) Perdew et al. Phys Rev Lett 77:3865, 1996 generalized functional were used in the geometry optimization and calculation process to calculate the exchange–correlation potential between electrons. The effect of coverage on the electronic and optical properties of the Be3N2-adsorbed O atom system was investigated by adsorbing different numbers of O atoms on a monolayer of Be3N2. The Be3N2 protocell contains two N atoms and three Be atoms with a space community of P6/MMM (No.191). The original cell was expanded 3 times along the direction of the base vectors a and b in the Be3N2 plane to create a 3 × 3 × 1 monolayer Be3N2 supercell system. A vacuum layer of 15 Å is set in the direction of the crystal plane of the vertical monolayer Be3N2 supercell to eliminate interactions between adjacent layers. In the overall energy convergence test of the Be3N2 supercell, the plane wave truncation energy was set to 500 eV, and the energy difference between the calculations given in the literature Reyes-Serrato et al. J Phys Chem Solids 59:743-6, 1998 using 550 eV was less than 0.01 eV, verifying the reliability of the data at a truncation energy of 500 eV. The Monkhorst–Pack special k-point sampling method Monkhorst et al. Phys Rev B 13:5188, 1976 was used in the structural calculations, and the grid was set to 3 × 3 × 1. The geometric optimization parameters are set as follows: the self-consistent field iteration convergence criterion is 2.0 × 10−6 eV, and the iterative accuracy convergence value is not less than 1.0 × 10−5 eV/atom for the total force of each atom and less than 0.03 eV/Å for all atomic forces. In addition the high-symmetry k-point path is taken as Γ(0,0,0) → M(0,0.5,0) → K(− 1/3,2/3,0) → Γ(0,0,0) Chen et al, AIP Adv 8:105105, 2018. [ABSTRACT FROM AUTHOR]

Context: In this paper, the optimum coverage of 4.44% and the optimum adsorption sites were determined for the Be3N2 adsorption system of O atoms at different coverages based on density functional theory. The electronic and optical properties of the model were investigated by applying bending deformation to the model at these coverage and adsorption sites. Adsorption of O atoms disrupts the geometrical symmetry of Be3N2, resulting in orbital rehybridization and lowering its band gap. Bending deformation causes the band gap of the adsorbed O atom structure of Be3N2 to first increase and then decrease, resulting in the modulation of its band gap. With increasing bending deformation, the adsorbed system is redshifts, and the degree of redshift increases with increasing bending deformation. Methods: All calculations in this paper were performed using the first-principles-based CASTEP module of Materials Studio (MS). The generalized gradient approximation (GGA) plane-wave pseudopotential method and the Perdew-Burke-Ernzerhof (PBE) Perdew et al. Phys Rev Lett 77:3865, 1996 generalized functional were used in the geometry optimization and calculation process to calculate the exchange–correlation potential between electrons. The effect of coverage on the electronic and optical properties of the Be3N2-adsorbed O atom system was investigated by adsorbing different numbers of O atoms on a monolayer of Be3N2. The Be3N2 protocell contains two N atoms and three Be atoms with a space community of P6/MMM (No.191). The original cell was expanded 3 times along the direction of the base vectors a and b in the Be3N2 plane to create a 3 × 3 × 1 monolayer Be3N2 supercell system. A vacuum layer of 15 Å is set in the direction of the crystal plane of the vertical monolayer Be3N2 supercell to eliminate interactions between adjacent layers. In the overall energy convergence test of the Be3N2 supercell, the plane wave truncation energy was set to 500 eV, and the energy difference between the calculations given in the literature Reyes-Serrato et al. J Phys Chem Solids 59:743-6, 1998 using 550 eV was less than 0.01 eV, verifying the reliability of the data at a truncation energy of 500 eV. The Monkhorst–Pack special k-point sampling method Monkhorst et al. Phys Rev B 13:5188, 1976 was used in the structural calculations, and the grid was set to 3 × 3 × 1. The geometric optimization parameters are set as follows: the self-consistent field iteration convergence criterion is 2.0 × 10−6 eV, and the iterative accuracy convergence value is not less than 1.0 × 10−5 eV/atom for the total force of each atom and less than 0.03 eV/Å for all atomic forces. In addition the high-symmetry k-point path is taken as Γ(0,0,0) → M(0,0.5,0) → K(− 1/3,2/3,0) → Γ(0,0,0) Chen et al, AIP Adv 8:105105, 2018. [ABSTRACT FROM AUTHOR]

We have simulated the effect of changing the end groups in BTP core with five organic units of 1,3-Indandione (IN), 2-thioxothiazolidin-4-one (Rhodanine), propanedinitrile (Malononitrile), (2-(6-oxo-5,6-dihydro-4H-cyclopenta[c]thiophen-4-ylidene)malononitrile) (CPTCN) and 2-(3-oxo-2,3-dihydroinden-1-ylidene (IC), and two halogenated units of (4F) IC and (4Cl) IC on the optical and photovoltaic properties of the BTP DA'D core molecular unit. Thus modified, seven molecular structures are considered and their optical properties, including HOMO and LUMO energies and absorption spectra are simulated in this paper. On the basis of HOMO and LUMO energies, it is found that two of the seven molecules, BTP-IN and BTP-Rhodanine, can act as donors and the other four, BTP-(4F) IC, BTP-(4Cl) IC, BTP-CPTCN and BTP-IC, as acceptors in designing bulk heterojunction (BHJ) organic solar cells (OSCs). Using these combinations of donors and acceptors in the active layer, eight BHJ OSCs, such as BTP-IN: BTP-(4F) IC, BTP-IN: BTP-(4Cl) IC, BTP-IN: BTP-CPTCN, BTP-IN: BTP-IC, BTP-Rhodanine: BTP-(4F) IC, BTP-Rhodanine: BTP-(4Cl) IC, BTP-Rhodanine: BTP-CPTCN and BTP-Rhodanine: BTP-IC, are designed, and their photovoltaic performance is simulated. The photovoltaic parameters J s c , V o c and FF for all eight BHJ OSCs and their power conversion efficiency (PCE) are simulated. It is found that the BHJ OSC of the BTP-IN: BTP-CPTCN donor–acceptor blend gives the highest PCE (14.73%) and that of BTP-Rhodanine: BTP-(4F) IC gives the lowest PCE (12.07%). These results offer promising prospects for the fabrication of high-efficiency BHJ OSCs with the blend of both donor and acceptor based on the same core structure. [ABSTRACT FROM AUTHOR]

Context: The electronic properties and optical properties of Cr-doped monolayer WS2 under uniaxial compressive deformation have been investigated based on density functional theory. In terms of electronic structure properties, both intrinsic and doped system bandgaps decrease with the increase of compression deformation, and the values of the bandgap under the same compression deformation after Cr doping are reduced compared with the corresponding intrinsic states. When the compressive deformation reaches 10%, both the intrinsic and doped system band gaps are close to zero. New electronic states and impurity energy levels appear in the WS2 system when doped with Cr atoms. For the optical properties, the calculation and analysis of the dielectric function under each deformation regime of monolayer WS2 show that the compression deformation affects the dielectric function, and when the compression deformation is 10%, the un-doped and Cr-doped regimes show a decrease in ε1(ω) compared to the compression deformation of 8%. For each deformation system, the peak reflections occur in the ultraviolet region. Near the position where the second peak of the absorption spectrum appears, it can be seen that the ability of each system to absorb light gradually decreases with the increase of the amount of deformation and appears to be red-shifted to varying degrees. Methods: This study follows the initial principles of the density functional theory framework and is based on the CASTEP module of Materials-Studio software GGA and PBE generalizations are used to perform computations such as geometry optimization of the model. We have calculated the energy band structure of monolayer WS2 with intrinsic and compressive deformations of 2% and 4% using PBE and HSE06, respectively. The band gap values calculated using PBE are 1.802 eV, 1.663 eV, and 1.353 eV, respectively, and the band gap values calculated with HSE06 are 2.267 eV, 2.034 eV, 1.751 eV. The results show that the bandgap values calculated by HSE06 are significantly higher than those calculated by PBE, but the bandgap variations calculated by the two methods have the same trend, and the shape characteristics of the energy band structure are also the same. However, it is worth noting that the computation time required for the HSE06 calculation is much longer than that of the PBE, which is far beyond the capability of our computer hardware, and the purpose of this paper is to investigate the change rule of the effect of deformation on the bandgap value, so to save the computational resources, the next calculations are all calculated using the PBE. The Monkhorst–Pack special K-point sampling method is used in the calculations. The cutoff energy for the plane wave expansion is 400 eV, and the K-point grid is assumed to be 5 × 5 × 1. Following geometric optimization, the iterative precision converges to a value of less than 0.03 eV/Å for all atomic forces and at least 1 × 10−5 eV/atom for the total energy of each atom. The vacuum layer's thickness was selected at 20 Å to mitigate the impact of the interlayer contact force. [ABSTRACT FROM AUTHOR]

Context: The electronic properties and optical properties of Cr-doped monolayer WS2 under uniaxial compressive deformation have been investigated based on density functional theory. In terms of electronic structure properties, both intrinsic and doped system bandgaps decrease with the increase of compression deformation, and the values of the bandgap under the same compression deformation after Cr doping are reduced compared with the corresponding intrinsic states. When the compressive deformation reaches 10%, both the intrinsic and doped system band gaps are close to zero. New electronic states and impurity energy levels appear in the WS2 system when doped with Cr atoms. For the optical properties, the calculation and analysis of the dielectric function under each deformation regime of monolayer WS2 show that the compression deformation affects the dielectric function, and when the compression deformation is 10%, the un-doped and Cr-doped regimes show a decrease in ε1(ω) compared to the compression deformation of 8%. For each deformation system, the peak reflections occur in the ultraviolet region. Near the position where the second peak of the absorption spectrum appears, it can be seen that the ability of each system to absorb light gradually decreases with the increase of the amount of deformation and appears to be red-shifted to varying degrees. Methods: This study follows the initial principles of the density functional theory framework and is based on the CASTEP module of Materials-Studio software GGA and PBE generalizations are used to perform computations such as geometry optimization of the model. We have calculated the energy band structure of monolayer WS2 with intrinsic and compressive deformations of 2% and 4% using PBE and HSE06, respectively. The band gap values calculated using PBE are 1.802 eV, 1.663 eV, and 1.353 eV, respectively, and the band gap values calculated with HSE06 are 2.267 eV, 2.034 eV, 1.751 eV. The results show that the bandgap values calculated by HSE06 are significantly higher than those calculated by PBE, but the bandgap variations calculated by the two methods have the same trend, and the shape characteristics of the energy band structure are also the same. However, it is worth noting that the computation time required for the HSE06 calculation is much longer than that of the PBE, which is far beyond the capability of our computer hardware, and the purpose of this paper is to investigate the change rule of the effect of deformation on the bandgap value, so to save the computational resources, the next calculations are all calculated using the PBE. The Monkhorst–Pack special K-point sampling method is used in the calculations. The cutoff energy for the plane wave expansion is 400 eV, and the K-point grid is assumed to be 5 × 5 × 1. Following geometric optimization, the iterative precision converges to a value of less than 0.03 eV/Å for all atomic forces and at least 1 × 10−5 eV/atom for the total energy of each atom. The vacuum layer's thickness was selected at 20 Å to mitigate the impact of the interlayer contact force. [ABSTRACT FROM AUTHOR]

The Dirac cone in the single-layer graphene limits its application in electronic devices such as Schottky barrier diodes and field-effect transistors. Thus, we make the novel heterostructures based on graphene to solve this problem. The electronic and optical properties of pristine and Ag/Au/Cu-doped graphene/MoS 2 heterostructures are investigated by using the density functional theory. For the Ag/Au/Cu-doped MoS 2 monolayer, the results show that they are magnetic. Their bands across the Fermi level, which indicates these systems are metallic. For the Ag/Au/Cu-doped graphene/MoS 2 heterostructures, they are metallic and nonmagnetic. Especially in the Au-doped graphene/MoS 2 , the Dirac cone opens about 66 meV. It means that Au-doped graphene/MoS 2 has the potential to be a candidate material for high speed electronic devices. Compared with pristine heterostructure, the probability of electron transition in the low energy region is the enhanced in Ag/Au/Cu-doped systems. The optical absorption coefficient of doped heterostructure is enhanced in the range of 0–0.4 eV and 1.7–2.7 eV. This work indicates that these heterostructures have a certain potential in the application of nanodevices. [Display omitted] • This paper confirms that the graphene can adsorb on Ag/Au/Cu-doped MoS 2 monolayer stably. • This paper finds that the Dirac cone in the Au-doped graphene/MoS 2 heterostructure opens about 66 meV. • The introduction of Ag/Au/Cu atoms in graphene/MoS 2 heterostructure can make the electron transfer at low energy. • The optical absorption coefficient is improved in these doped heterostructures. [ABSTRACT FROM AUTHOR]

Graphene nanoribbons (GNRs), categorized into zigzag and armchair types, hold significant promise in electronics due to their unique properties. In this study, optical properties of zigzag and armchair GNRs are investigated using density functional theory (DFT) in conjunction with Kubo–Greenwood formalism. Our findings reveal that optical characteristics of both GNR types can be extensively modulated through the application of a transverse electric field, e.g., the refractive index of the a zigzag GNR is shown to vary in the range of n = 0.3 and n = 9.9 for the transverse electric field values between 0 V/Å and 10 V/Å. Additionally, electrical transmission spectra and the electrical conductivities of the GNRs are studied using DFT combined with non-equilibrium Green's function formalism, again uncovering a strong dependence on the transverse electric field. For example, the conductance of the armchair GNR is shown to vary in the range of G = 6 μA/V and G = 201 μA/V by the transverse electric field. These results demonstrate the potential of GNRs for use in electronically controlled optoelectronic devices, promising a broad range of applications in advanced electronic systems. [ABSTRACT FROM AUTHOR]

Modifying electrical and optical properties in two-carbon materials is essential for electronic devices, energy storage and biosensor applications. We report a comparative study of the effect of systematically intercalated strontium atoms in AA- and AB-stacked bilayer graphene (BG) in the framework of density functional theory (DFT). The electronic band structures, the total and partial electronic density of states and the dielectric function are studied. We show that the intercalation of atoms can influence both electronic properties. Our results show that the Dirac cones, a signature of graphene, are translated into the conduction band. This property may be useful in band-gap tuning applications of nanodevices. The optical properties were calculated parallel and perpendicular to the graphene sheet under polarised electric fields. The calculated optical properties show that the intercalation of Sr in the AA- and AB-stacked BGs promotes IR absorption. The findings provide a basis for developing graphene intercalary compounds, which can be used in optoelectronics to control the absorption of light wavelengths and specifically in biosensor applications. [ABSTRACT FROM AUTHOR]

Density Functional Theory is employed to investigate how specific rare earth (RE) dopants (Pr, Y, Dy) affect the electronic, magnetic, and optical characteristics of Co0.5Ni0.5Fe2O4 (CN) spinel ferrites. The impact of RE atoms, which replace Fe ions in the supercell, is elucidated by analyzing the spin-resolved density of states, magnetic moment, and optical parameters. The findings demonstrate that both single and collective RE doping play a vital role in manipulating the key properties of these materials. Notably, we reveal that incorporating RE dopants into CN structures leads to a reduction in the energy band gap. Additionally, this work underscores substantial spin-dependent behavior and provides valuable insights into optical properties, suggesting that RE-doped CNs hold significant potential in the fields of spintronics and optoelectronics. [ABSTRACT FROM AUTHOR]

First principles calculations of the structural, electronic and optical properties of GaSb, InSb and their ternary Ga 1 - x In x Sb alloys (x = 0.25, 0.50 and 0.75) have been performed using the full-potential linear muffin-tin orbital (FP-LAPW) method within density functional theory (DFT). The generalized gradient approximation and modified Becke and Janson functional with local density approximation (mBJ–LDA) are utilized for the treatment of exchange and correlation potentials. The results show the calculated lattice constants increase linearity with increasing the In concentration. The electronic band structure indicates that these alloys are direct band gap semiconductors for all the values of x and the band gap decreases as x increases from x = 0 to x = 1. The results also show that the there is a non-linear dependence of the band gap on composition x in Ga 1 - x In x Sb alloys. Regarding optical properties, the real and imaginary parts of the dielectric function have been calculated. The results show that the static dielectric constant increases with increase in concentration of In, consistent with reduction in energy band gap. The onset point and major peaks in the imaginary parts of the dielectric function spectra are identified for the Ga 1 - x In x Sb alloys and shown that they are related to the corresponding band gap values. The results also show that for energy values higher than ≅ 4 eV, the electromagnetic wave transition through Ga 1 - x In x Sb alloys is nearly zero. [ABSTRACT FROM AUTHOR]

The structural, electronic, magnetic, and optical properties of Co-doped 10–20-atom silver clusters are investigated by GGA/PBE via the density functional theory. The Ag–Co clusters form core–shell structures with a Co atom in the center. Co atom doping modulates electronic properties like energy gap, molecular softness, global hardness, electronegativity, and electrophilicity index. For the optical spectra of the Ag–Co clusters, the energy of their spectra overall exhibits little change with increasing numbers of atoms; the strongest peaks are roughly distributed at 3.5 eV, and the intensity of their spectra overall is strengthened. Raman and vibrational spectra reflect structural changes with Co atom addition. The addition of the Co atom alters magnetic moments of specific Ag–Co clusters, while others remain unchanged. [ABSTRACT FROM AUTHOR]

The structural stability analysis of various phases of GeTMS3(TM=Sc, Fe, Zn) sulfide perovskite has been conducted utilizing the WIEN2k package. This investigation leverages density functional theory (DFT) within the full potential linearized augmented plane wave (FP-LAPW) method, employing GGA-mBJ potentials. The focus of this study has encompassed the computation of structural, magnetic, and optical attributes across distinct GeTMS3 phases. These materials have been identified as promising contenders for applications in photovoltaics and spintronics. The study reveals the stability of various phases, with the orthorhombic phase proving energetically favorable for GeScS3 and GeZnS3, and the tetragonal phase for GeFeS3. Magnetic analyses indicate favorable ferromagnetic behavior in GeFeS3 and nonmagnetic characteristics in GeScS3 and GeZnS3. Furthermore, electronic examinations unveil semimetallic and semiconducting behaviors in GeScS3 and GeZnS3 in the tetragonal, respectively, with GeFeS3 exhibiting a half-metallic nature in the orthorhombic phase. Optical properties illustrate their potential as light harvesters, displaying characteristics suitable for energy conversion applications. This study contributes to a deeper understanding of sulfide perovskite properties, offering insights into potential applications in diverse technological fields. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) MXenes, having comparable transport properties like graphene and a wide spectrum application, are often limited to being used in optoelectronics due to metallic bandgap. Here, by employing density functional theory we report the bandgap engineering and tuning optoelectronic properties through modulating the anions of novel 2D spinel Hf3X2O2 (X = N, P and As) MXenes structures and show that the material class can be among the few semiconducting MXenes. Phonon spectra and cohesive energies confirm that these structures are dynamically stable and chemically exothermic. Modulating anions X = N, P, and As in Hf3X2O2, the electronic bandgaps are found ∼0.46 eV for N, metallic for P, and ∼48 meV for As atoms, suggesting the semiconducting, metallic, and semi-metallic MXenes. The biaxial strains are incorporated to tune the features: In the Hf3N2O2 structure, the bandgap is increased with both compressive and tensile strains, while for the Hf3As2O2 structure, the gap decreased at the GGA-PBE level. For Hf3P2O2 structures, the bandgaps are all metallic irrespective of pristine or biaxial strain. Spin–orbit coupling SOC+GGA reveals that Hf3N2O2 is highly spin responsive while Hf3As2O2 shows semi-metal-to-metallic bandgap transition for pristine as well as biaxial strained conditions. From optical properties analysis, optical absorptions are found located in the visible spectral regions that are also highly receptive to biaxial strains. These properties we have unleashed for the novel Hf3X2O2 (X = N, P, As) semiconducting MXene, thus, show the potentiality of the utilization of the material class in nanoelectronics and optoelectronics applications. [ABSTRACT FROM AUTHOR]

In this work, the optoelectronic properties of the getchellite crystal, a layered semiconducting disordered alloy with the chemical formula AsSbS3, are probed by a combination of complementary spectroscopic techniques, i.e., x-ray photoelectron spectroscopy together with a photoreflectance and a transmission spectroscopy. The experimental results are supported by a calculation based on density functional theory (DFT). The sample is an intrinsically p-type semiconductor whose optical properties are dominated by a direct transition. The energy of this transition is highly decreasing, by 0.22 eV, when the sample temperature increases from 20 to 300 K. A calculated band structure together with the transmission results reveals that of about 50 meV below the direct optical transition, an indirect one occurs associated with the fundamental bandgap of AsSbS3. Finally, the change in the fundamental bandgap character from indirect to direct during the reduction in material thickness from bulk to monolayer is demonstrated by the DFT calculations. [ABSTRACT FROM AUTHOR]

In this paper, a new type of Ba 2 La 8 (SiO 4) 6 O 2 : Sm3+ phosphor was synthesized by solid-phase reaction, and the hydrophobic agent was used to restrain the hydrolysis of silicate phosphor. The microstructure, optical properties and electroluminescence properties of the samples were systematically analyzed. The results show that the Ba 2 La 8 (SiO 4) 6 O 2 : x Sm3+ phosphors have a strong orange-red emission at 600 nm, which corresponds to the 6G 5/2 →6H 7/2 energy level transition of Sm3+ ions. The optimal luminescence intensity was achieved at the dopant concentration of 10 mol%. The prepared phosphor has good thermal stability, the luminescence intensity at 423 K is still 85% of that at 298 K, and the internal quantum efficiency (IQE) is 22.59%. The ultraviolet-visible-near-infrared (UV–VIS–NIR) spectrum and the density functional theory reveal that the Ba 2 La 8 (SiO 4) 6 O 2 host can provide an excellent band-gap environment for the luminescent center. In addition, the modified Ba 2 La 8 (SiO 4) 6 O 2 : 0.10Sm3+ phosphor showed excellent hydrophobicity and luminescent properties, with a contact angle of 140.315°, and the luminescent intensity remained 75% of the pre-modified level. The Ba 2 La 8 (SiO 4) 6 O 2 : Sm3+ phosphor has good dispersion in PVA solution and emits bright red light. The above properties indicate that Ba 2 La 8 (SiO 4) 6 O 2 : Sm3+ phosphor has excellent luminescence properties and has broad application prospects. [ABSTRACT FROM AUTHOR]

The alloying process plays a pivotal role in the development of advanced multifunctional plasmonic materials within the realm of modern nanotechnology. However, accurate in silico predictions are only available for metal clusters of just a few nanometers, while the support of modelling is required to navigate the broad landscape of components, structures and stoichiometry of plasmonic nanoalloys regardless of their size. Here we report on the accurate calculation and conceptual understanding of the optical properties of metastable alloys of both plasmonic (Au) and magnetic (Co) elements obtained through a tailored laser synthesis procedure. The model is based on the density functional theory calculation of the dielectric function with the Hubbard-corrected local density approximation, the correction for intrinsic size effects and use of classical electrodynamics. This approach is built to manage critical aspects in modelling of real samples, as spin polarization effects due to magnetic elements, short-range order variability, and size heterogeneity. The method provides accurate results also for other magnetic-plasmonic (Au-Fe) and typical plasmonic (Au-Ag) nanoalloys, thus being available for the investigation of several other nanomaterials waiting for assessment and exploitation in fundamental sectors such as quantum optics, magneto-optics, magneto-plasmonics, metamaterials, chiral catalysis and plasmon-enhanced catalysis. The optical properties of nanoalloys are complex and difficult to describe. Here, the authors use density functional and Mie theory to calculate the extinction of Au-Co and other nanoalloys of interest for quantum optics, magnetooptics, catalysis, and metamaterials. [ABSTRACT FROM AUTHOR]