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Context: The effect of X (X = O, Se, N, P, F, Cl) doping on the adsorption of Zn atoms by WS2 was investigated based on first principles. The electronic structure and optical properties of the adsorbed system after atomic doping were calculated. It is found that the Zn atom adsorbed on the W top (Tw) site has the most stable structure. When an S atom is replaced with an X atom based on the adsorption system, where the adsorption energy decreases after doping of O, P, F, and Cl atoms compared to the undoped system, it means that each system is more stable after doping of these atoms; charge transfer shows that the adsorption system after P-atom doping the system around the Zn atom loses electrons while S-atom gains electrons, which indicates that P-atom doping is favorable for the adsorption of Zn by WS2, N, P-atom is introduced as p-type doping and F, Cl-atom is introduced undoped by n-type doping, and the band gap of the doped system is less than that of the undoped one. With the introduction of different dopant atoms, certain impurity energy levels are introduced into the adsorption system. The prohibited bandwidth around the Fermi energy level reduces the density of states, causing the doped system's density of states to shift to lower energies, among which the shifts of N, P, F, and Cl are more pronounced. The P-doped adsorption system shows a new peak near the energy of − 11 eV. In addition, the study of optical properties showed that the peak reflections of both doped and non-doped systems adsorbing Zn atoms appeared in the ultraviolet region; the absorbance coefficient of the doped system is moved in the lower energy direction and red-shifted after atom doping; in addition, the absorption coefficients and reflectance of the P, Se doped systems are enhanced in the wavelength range of 200–300 nm compared with that before doping, the dielectric function and CBM and VBM positions were also calculated further indicating the potential of Se-doped systems in improving photocatalytic efficiency. Methods: In this paper, the structure optimization of X (X = O, Se, N, P, F, Cl) doping on WS2 adsorbed Zn atom model is performed based on the CASTEP module in Materials-Studio software under the first principles using GGA and PBE generalized function. The corresponding binding energies, bond lengths, bond angles, charge densities, energy band structures, densities of states, and optical properties were also analyzed. The Monkhorst–Pack particular K-point sampling method is used in the calculations; the K-point grid is 6 × 6 × 1, and the cutoff energy for the plane wave expansion is 500 eV. After geometric optimization, the iterative accuracy converges to a value of less than 1 × 10−5 eV/atom for the total energy of each atom and less than 0.03 eV/Å for all atomic forces. The thickness of the vacuum layer was set to 20 Å to avoid the effect of interlayer interaction forces. In this paper, 27 atoms were used to form a 3 × 3 × 1 supercellular tungsten disulfide system consisting of 18 S atoms and 9 W atoms. [ABSTRACT FROM AUTHOR]

Context: To lessen the impact of the dangerous metal Cr, this paper applies the first principles to investigate the adsorption behavior and photoelectric properties of GaS on Cr. The effects of doped GaS on Cr adsorption behavior are investigated with four GaS systems, which are pure, boron (B)-doped, nitrogen (N)-doped, and oxygen (O)-doped, in order to maximize the characteristics of GaS for use in novel sectors, to obtain understanding of the impact of doping on the electronic structure and optical properties of GaS adsorption of Cr, as well as to promote the development of the material. Four GaS adsorbed Cr systems, pure, B-doped, N-doped, and O-doped, are optimized, and the optimized results show that the stable adsorption position of Cr on both pure and doped GaS is the top position of Ga atoms, whereas doped elements B, N, and O can promote the adsorption of Cr on GaS, and the order of the strength of this promotion is B > N > O. Method: In this paper, molecular simulation calculations and analyses using the CASTEP module in the software Materials Studio are performed to simulate the structure optimization of GaS-adsorbed Cr materials doped with B, N, and O atoms by using the generalized gradient approximation (GGA) plane-wave pseudopotential approach [1] and the Perdew-Burke-Ernzerhof (PBE) generalized function [2]. From the convergence test, it is reasonable to set the K-point network to 4 × 4 × 1 and the truncation energy to 500 eV [3]. In this paper, a 3 × 3 × 1 supercell structure with 18 S atoms and 18 Ga atoms is selected. The convergence value of the iterative accuracy is 1.0e − 5 eV/atom, and all the atomic forces are less than 0.02 eV/Å. A vacuum layer of 16 Å is also set in the C direction to avoid interlayer interactions of GaS. First, we optimize the geometry of the model and then analyze the nature of the adsorption energy and electronic structure corresponding to the model. [ABSTRACT FROM AUTHOR]

Context: In this paper, the electronic and optical properties of Cr-doped monolayer MoS2 under uniaxial tensile strain are investigated by first-principle calculations. It is shown that uniaxial tensile strain can significantly change the electronic and optical properties of Cr-doped monolayer MoS2, and the bandgap value of the intrinsic MoS2 system gradually decreases with the increase of tensile strain, while the bandgap value of the Cr-doped MoS2 system is relatively stable. However, when the stretching reaches a certain degree, both the intrinsic and doped systems become metallic. From the analysis of the density of states, it is found that new electronic states and energy levels appear in the intrinsic MoS2 system and all Cr-doped monolayer MoS2 systems with the increase of the tensile strain, but the changes in the density of states diagrams of the Cr-doped monolayer MoS2 system are relatively small, which is mainly attributed to the effect of the Cr-doped atoms. The analysis of optical properties displays that the stretched doped system differs from the intrinsic MoS2 system in terms of dielectric function, absorption and reflection, energy loss function, and refractive index. Our results suggest that uniaxial tensile strain can be used as an effective means to modulate the electronic structure and optical properties of Cr-doped monolayer MoS2. These findings provide a theoretical basis for understanding the optoelectronic properties of MoS2 and its doped systems as well as their applications in optoelectronic devices. Methods: Based on the first principle of density functional theory framework and the CASTEP module in Materials Studio software (Perdew et al. in Phys Rev Lett 77(18):3865–3868, 1996). The structure of Cr atom-doped MoS2 systems and MoS2 systems were optimized using the generalized gradient approximation plane-wave pseudopotential method (GGA) and Perdew-Burke-Ernzerhof (PBE) generalized functions under 3%, 6%, and 9% tensile deformation, and the corresponding formation energy, bond length, electronic structure, and optical properties of the models were analyzed. The Grimme (J Comput Chem 27(15):1787–1799, 2006) vdW correction with 400 eV cutoff was used in Perdew-Burke-Ernzerhof (PBE) functional to optimize the geometry until the forces and energy converged to 0.02 eV/Å and 1.0e-5eV/atom, respectively. For each model structure optimization, the K-point grid was assumed to be 4×4×1, using the Monkhorst-Pack special K-point sampling method. After the MoS2 supercell convergence test, the plane-wave truncation energy was chosen to be 400 eV. Following geometric optimization, the iterative accuracy converged to no less than 1.0×10−5 eV/atom for total atomic energy and less than 0.02 eV/Å for all atomic forces. We created a vacuum layer of 18 Å along the Z-axis to prevent the impact of periodic boundary conditions and weak van der Waals forces between layers on the monolayer MoS2. In this paper, a total of 27 atoms were used for the 3×3×1 supercell MoS2 system, which consists of 18 S atoms and 9 Mo atoms. [ABSTRACT FROM AUTHOR]

Context: In this paper, the electronic and optical properties of Cr-doped monolayer MoS2 under uniaxial tensile strain are investigated by first-principle calculations. It is shown that uniaxial tensile strain can significantly change the electronic and optical properties of Cr-doped monolayer MoS2, and the bandgap value of the intrinsic MoS2 system gradually decreases with the increase of tensile strain, while the bandgap value of the Cr-doped MoS2 system is relatively stable. However, when the stretching reaches a certain degree, both the intrinsic and doped systems become metallic. From the analysis of the density of states, it is found that new electronic states and energy levels appear in the intrinsic MoS2 system and all Cr-doped monolayer MoS2 systems with the increase of the tensile strain, but the changes in the density of states diagrams of the Cr-doped monolayer MoS2 system are relatively small, which is mainly attributed to the effect of the Cr-doped atoms. The analysis of optical properties displays that the stretched doped system differs from the intrinsic MoS2 system in terms of dielectric function, absorption and reflection, energy loss function, and refractive index. Our results suggest that uniaxial tensile strain can be used as an effective means to modulate the electronic structure and optical properties of Cr-doped monolayer MoS2. These findings provide a theoretical basis for understanding the optoelectronic properties of MoS2 and its doped systems as well as their applications in optoelectronic devices. Methods: Based on the first principle of density functional theory framework and the CASTEP module in Materials Studio software (Perdew et al. in Phys Rev Lett 77(18):3865–3868, 1996). The structure of Cr atom-doped MoS2 systems and MoS2 systems were optimized using the generalized gradient approximation plane-wave pseudopotential method (GGA) and Perdew-Burke-Ernzerhof (PBE) generalized functions under 3%, 6%, and 9% tensile deformation, and the corresponding formation energy, bond length, electronic structure, and optical properties of the models were analyzed. The Grimme (J Comput Chem 27(15):1787–1799, 2006) vdW correction with 400 eV cutoff was used in Perdew-Burke-Ernzerhof (PBE) functional to optimize the geometry until the forces and energy converged to 0.02 eV/Å and 1.0e-5eV/atom, respectively. For each model structure optimization, the K-point grid was assumed to be 4×4×1, using the Monkhorst-Pack special K-point sampling method. After the MoS2 supercell convergence test, the plane-wave truncation energy was chosen to be 400 eV. Following geometric optimization, the iterative accuracy converged to no less than 1.0×10−5 eV/atom for total atomic energy and less than 0.02 eV/Å for all atomic forces. We created a vacuum layer of 18 Å along the Z-axis to prevent the impact of periodic boundary conditions and weak van der Waals forces between layers on the monolayer MoS2. In this paper, a total of 27 atoms were used for the 3×3×1 supercell MoS2 system, which consists of 18 S atoms and 9 Mo atoms. [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]

Purposes: The paper aims to investigative the cacuses and impacts of In- and Vacancy-doped to 6H-SiC, expecting that improving optical properties of materials. Design-Using the first-principles calculations, we discuss the electronic structure and optical properties of different doped 6H-SiC systems. Findings: The results show that In-doped 6H-SiC becomes a direct bandgap p-type semiconductor and the energy bandgap is reduced from the intrinsic 2.059 to 1.515 eV. We demonstrate the stability of the systems through the formation energy analysis, meanwhile identify their physical origins and discuss applications of all structures in electronic devices within optical analysis. Find the energy beginning values of the VSi-doped and VC-doped systems' optical absorption spectrums and extend to 0.4 2 eV and 0.11 eV respectively compared with the original 3.23 eV. In the visible light region, the reflectivity images of the VC/VSi and (In, VSi)-codoped systems rise obviously. Conclusions: The optical properties of all doping systems were analyzed to be improved compared with the intrinsic, all above mentioned provide a theoretical basis for the fabrication of spintronic and optical devices. [ABSTRACT FROM AUTHOR]

In this paper, we present the calculation results of the electronic structure and optical spectrum and an experimental study of the optical properties of Heusler alloys Mn2 –xFe1 +xAl (x = –0.5, 0, 0.5, 1). An anomalous for metallic systems behavior of the optical conductivity of alloys in the IR region of the spectrum was found: the absence of Drude growth and a high level of interband absorption. This behavior is shown to be determined by the features of the electronic structure: the Fermi level is located in the region of high density of states that is formed by the d states of Mn and Fe. [ABSTRACT FROM AUTHOR]

This paper presents electronic spectrum calculations and a study of the optical properties of the binary compounds Mn70Al30 and Mn80Al20 with the β-Mn structure. The energy dependences of the calculated density of states, with high values at the Fermi level, are determined by broad bands formed by manganese 3d states. The calculated electronic structures are used to analyze measured optical conductivity spectra of the alloys in the quantum light absorption range. From their optical properties in the infrared spectral region, we evaluate a number of characteristics of conduction electrons. [ABSTRACT FROM AUTHOR]

Context: In this study, the effects of different shear deformations on the structural stability, electronic structure, and optical properties of a Mg atom adsorption system of S vacancy defect SnS2 are systematically investigated based on density functional theory. It is shown that the presence of an S-vacancy defect makes the band gap of the SnS2 system significantly smaller than that of the perfect SnS2 system, and the SnS2 system is changed from a direct band gap semiconductor to an indirect band gap semiconductor. The optimal adsorption position of a Mg atom on the S-vacancy SnS2 system is above the S atom where the adsorption energy is the largest and the system is the most stable. The density of states of the adsorption system is predominantly contributed by the S-3p and Sn-5 s orbital electrons. The imposition of shear deformation leads to the introduction of certain impurity energy levels in the adsorption system, and the forbidden bandwidth near the Fermi energy level decreases. As compared to the intrinsic SnS2, the absorption and reflection peaks of adsorption systems under different shear deformation are red-shifted and appear in the ultraviolet region. This improves the utilization of the adsorption system for ultraviolet light to a great extent. Methods: The model calculations in this paper are performed using the CASTEP module of the Material Studio (MS) software based on the first principles of Density Functional Theory (DFT) (Wei et al. in Physica B 545:99–106, 2018) for plane wave artifacts. Geometrical optimization and computational procedures are used to calculate the exchange–correlation energy using the Perdew-Burke-Ernzerhof (PBE) generalized function (Perdew et al. in Phys Rev B Condens Matter 48:4978, 1993) of the generalized gradient approximation (GGA). The Monkhorst–Pack method (Monkhorst and Pack in Phys Rev B 13:5188–5192, 1976) was used to rationalize the sampling of the highly symmetric k-points in the Brillouin zone. The grid of k-points is set to be 6 × 6 × 1. The plane-wave truncation energy is set to be 400 eV. The energy convergence criterion is 1.0 × 10−5 eV. The residual stress of all atoms is 0.01 eV/Å. A vacuum layer with a thickness of 15 Å is set up in the z-direction, which ensures that the interactions of the system along the z-axis between the top and the bottom layers can be ignored during the whole simulation process. We construct a 3 × 3 × 1 SnS2 system containing 27 atoms as the computational model. The intrinsic SnS2 contains 9 Sn atoms and 18 S atoms. [ABSTRACT FROM AUTHOR]

Context: In this study, the effects of different shear deformations on the structural stability, electronic structure, and optical properties of a Mg atom adsorption system of S vacancy defect SnS2 are systematically investigated based on density functional theory. It is shown that the presence of an S-vacancy defect makes the band gap of the SnS2 system significantly smaller than that of the perfect SnS2 system, and the SnS2 system is changed from a direct band gap semiconductor to an indirect band gap semiconductor. The optimal adsorption position of a Mg atom on the S-vacancy SnS2 system is above the S atom where the adsorption energy is the largest and the system is the most stable. The density of states of the adsorption system is predominantly contributed by the S-3p and Sn-5 s orbital electrons. The imposition of shear deformation leads to the introduction of certain impurity energy levels in the adsorption system, and the forbidden bandwidth near the Fermi energy level decreases. As compared to the intrinsic SnS2, the absorption and reflection peaks of adsorption systems under different shear deformation are red-shifted and appear in the ultraviolet region. This improves the utilization of the adsorption system for ultraviolet light to a great extent. Methods: The model calculations in this paper are performed using the CASTEP module of the Material Studio (MS) software based on the first principles of Density Functional Theory (DFT) (Wei et al. in Physica B 545:99–106, 2018) for plane wave artifacts. Geometrical optimization and computational procedures are used to calculate the exchange–correlation energy using the Perdew-Burke-Ernzerhof (PBE) generalized function (Perdew et al. in Phys Rev B Condens Matter 48:4978, 1993) of the generalized gradient approximation (GGA). The Monkhorst–Pack method (Monkhorst and Pack in Phys Rev B 13:5188–5192, 1976) was used to rationalize the sampling of the highly symmetric k-points in the Brillouin zone. The grid of k-points is set to be 6 × 6 × 1. The plane-wave truncation energy is set to be 400 eV. The energy convergence criterion is 1.0 × 10−5 eV. The residual stress of all atoms is 0.01 eV/Å. A vacuum layer with a thickness of 15 Å is set up in the z-direction, which ensures that the interactions of the system along the z-axis between the top and the bottom layers can be ignored during the whole simulation process. We construct a 3 × 3 × 1 SnS2 system containing 27 atoms as the computational model. The intrinsic SnS2 contains 9 Sn atoms and 18 S atoms. [ABSTRACT FROM AUTHOR]

Theoretical studies on CdS/BiOI heterojunctions are lacking; therefore, this paper studies their electronic structure and optical properties through density functional theory calculations. First-principles calculations were made to investigate the effect of introducing oxygen vacancy defects on the photocatalytic efficiency of CdS/BiOI. The band gap of CdS/BiOI was effectively narrowed compared to that of its constituent materials, resulting in a redshift of the absorption edge. Based on the obtained work functions, the difference in Fermi energy levels caused a spontaneous flow of electrons, resulting in band bending and the establishment of a local electric field. The electric field promoted the separation of electron–hole pairs. At the same time, the addition of oxygen vacancies created impurity levels, allowing light absorption to extend to the infrared region, further promoting carrier separation. Our study reveals the origin of the enhanced efficiency of CdS/BiOI heterostructures and also predicts the photocatalytic activity of CdS/BiOI heterojunctions after introducing oxygen vacancies. These results may facilitate the design of such structures with enhanced photocatalytic properties. • The electronic structure and optical properties of CdS/BiOI heterojunction are studied by using density functional theory, and the effect of introducing oxygen vacancy defects into the structure is predicted theoretically. • According to the band structure, density of state, 3D/2D charge density difference and work function calculated by the first principle, the electron transfer from BiOI to CdS can be analyzed, and the trend is enhanced after the introduction of oxygen vacancy defect. • The calculation of optical properties shows that the formation of heterojunction and the introduction of oxygen vacancy defects promote the enhancement of optical absorption intensity. • This paper supplements the theoretical calculation of vacancy in CdS/BiOI heterojunction. And defects are introduced into the heterostructure to enhance the catalytic performance of such materials. [ABSTRACT FROM AUTHOR]

This paper employs the Heyd-Scuseria-Ernzerhof (HSE) function to research electronic structures of monolayer InxAl1-xN with different compositions (x = 0, 0.25, 0.5, 0.75, 1) based on the first-principles, and the optical properties of singlelayer InxAl1-xN are calculated by Generalized Gradient Approximation-Perdew Burke Ernzerhof (GGA-PBE) function. The influence of the electronic structure on the properties has been analyzed. Then the influence of doping quantity on the characteristics has been summarized, which also indicates the trend of the complex dielectric function and absorption spectrum. The calculation results show that with the increase of x, the static dielectric constant increases, the electron transition ability increases, and the absorption peak intensity in the light absorption spectrum increases. It can conclude that the InxAl1-xN compound can theoretically achieve the adjustable Eg and photoelectric performance with x, which will apply in making various optoelectronic devices, including solar cells and sensors. [ABSTRACT FROM AUTHOR]

Van der Waals (vdW) heterostructures provide an effective strategy for exploring and expanding the potential applications of two-dimensional materials. In this study, we employ first-principles density functional theory (DFT) to investigate the geometric, electronic, and optical properties of MoGe2N4/AlN and MoSiGeN4/AlN vdW heterostructures. The stable MoGe2N4/AlN heterostructure exhibits an indirect band gap semiconductor with a type-I band gap arrangement, making it suitable for optoelectronic devices. Conversely, the stable MoSiGeN4/AlN heterostructure demonstrates various band gap arrangements depending on stacking modes, rendering it suitable for photocatalysis applications. Additionally, we analyze the effects of mechanical strain and vertical electric field on the electronic properties of these heterostructures. Our results indicate that both mechanical strain and vertical electric field can adjust the band gap. Notably, application of an electric field or mechanical strain leads to the transformation of the MoGe2N4/AlN heterostructure from a type-I to a type-II band alignment and from an indirect to a direct band transfer, while MoSiGeN4/AlN can transition from a type-II to a type-I band alignment. Type-II band alignment is considered a feasible scheme for photocatalysis, photocells, and photovoltaics. The discovery of these characteristics suggests that MoGe2N4/AlN and MoSiGeN4/AlN vdW heterostructures, despite their high lattice mismatch, hold promise as tunable optoelectronic materials with excellent performance in optoelectronic devices and photocatalysis. [ABSTRACT FROM AUTHOR]

Using first principles calculations based on the density functional theory and the structural, electronic, and optical properties of the substitution of K elements by Li+, Na+, Mg2+, and Ca2+ in KH2PO4 (KDP) crystals are investigated in depth. This study provides insight into the structural properties of crystals, with particular emphasis on internal chemical bonding effects. It further discusses the impact of H and O defects on the bandgap and optical properties of KDP crystals. Detailed analysis of structural characteristics and comprehensive examination of the effects of chemical bonds contribute to a deeper understanding of the effects of defects on the lattice and electronic structure, revealing potential alterations and their underlying mechanisms. Our investigation focuses on the regulatory role of different defects on the bandgap and optical properties. These comprehensive analyses provide a more thorough understanding of the impact of defects on the properties of KDP crystals, establishing an essential research foundation for further exploration of nonlinear optics crystal potential applications. [ABSTRACT FROM AUTHOR]

In this study, we comprehensively explored the electronic structure and optical properties of Ni-doped Bi4O5Br2 through first-principles computational calculations. By calculating its electronic structure and band characteristics, we investigated the impact of Ni doping on the photocatalytic performance of Bi4O5Br2. The computational results indicated that Ni doping significantly altered the band structure of Bi4O5Br2, leading to a reduction in the band gap width. The band gap for undoped Bi4O5Br2 was 2.151 eV, whereas the Ni-doped system exhibited a smaller band gap, directly indicating its enhanced visible light absorption capacity and facilitating the effective separation of photo-generated electron–hole pairs. Through analysis of 2D charge density maps, we observed changes in chemical bonding induced by Ni doping. The shortening of Ni-O bonds suggested increased bond strength, consistent with the observed reduction in cell volume. These findings provide a theoretical foundation for understanding the mechanisms behind the enhanced photocatalytic hydrogen production performance in Ni-doped Bi4O5Br2, offering valuable insights for the design and optimization of highly efficient photocatalytic materials. [ABSTRACT FROM AUTHOR]

We utilized a first-principle density functional theory for a comprehensive analysis of CsPbX3 (X = F, Cl, Br, I) to explore its physical and chemical properties, including its mechanical behavior, electronic structure and optical properties. Calculations show that all four materials have good stability, modulus of elasticity, hardness and wear resistance. Additionally, CsPbX3 demonstrates a vertical electron leap and serves as a semiconductor material with direct band gaps of 3.600 eV, 3.111 eV, 2.538 eV and 2.085 eV. In examining its optical properties, we observed that the real and imaginary components of the dielectric function exhibit peaks within the low-energy range. Furthermore, the dielectric function gradually decreases as the photon energy increases. The absorption spectrum reveals that the CsPbX3 material exhibits the highest UV light absorption, and as X changes (with the increase in atomic radius within the halogen group of elements), the light absorption undergoes a red shift, becoming stronger and enhancing light utilization. These properties underscore the material's potential for application in microelectronic and optoelectronic device production. Moreover, they provide a theoretical reference for future investigations into CsPbX3 materials. [ABSTRACT FROM AUTHOR]

Hydrogen boride (HB), a freestanding 2D hydrogenated‐borophene (borophane) polymorph, is synthesized via ion exchange. HB sheets with a B/H atomic ratio of 1.0 are confirmed to contain three‐center–two‐electron B–H–B bonds and two‐center–two‐electron terminal B–H bonds. The optical properties of HB sheets are expected to be tunable by changing the BHB/BH bond ratio, which alters the electronic structure of HB sheets; however, this is not yet achieved. This study demonstrates that controlling the BHB/BH bond ratio in the HB sheets is possible without altering the hydrogen content by adjusting the volume of ion‐exchange resin during synthesis, thus enabling the tuning of the photoinduced H2 release under UV irradiation. Furthermore, the fluorescence intensity correlates with the absorbance ratio of the BHB and BH vibrational modes. Increasing the BHB/BH bond ratio enhances the luminescence intensity, whereas reducing it enhances the photoinduced H2 release rate under UV irradiation. The ability to control the BHB/BH bond ratio of HB sheets provides new avenues for optimizing their properties for various applications, including hydrogen storage and photocatalysis. [ABSTRACT FROM AUTHOR]

We present a comprehensive study on the structural, electronic, and optical properties of V x A l 1 − x N ternary alloys using first-principles calculations. Our investigations employ the full-potential linearized augmented-plane-wave (FP-LAPW) method within the density functional theory (DFT) framework. The impact of varying vanadium composition (x = 0, 0.25, 0.5, 0.75, 1) on the structural, electronic, and optical characteristics of wurtzite V x A l 1 − x N alloys is examined in detail. Our findings reveal a distinct nonlinear relationship between the lattice constant, bulk modulus, and the concentration of vanadium (x) in the V x A l 1 − x N alloys. An analysis of the electronic band structures and densities of states reveals a metallic behavior in the V x A l 1 − x N alloys, primarily driven by the V-d states near the Fermi energy. These results shed light on the electronic properties of the alloys, contributing to a deeper understanding of their potential for various applications. Furthermore, we calculate various optical properties, including the real and imaginary dielectric functions, refractive index, energy loss spectrum, and reflectivity. The obtained optical functions provide valuable insights into the optical behavior of the V x A l 1 − x N alloys. The results contribute to the fundamental knowledge of these materials and their potential applications in various fields. [ABSTRACT FROM AUTHOR]

The energy band structure, density of states, and optical properties of monolayers of MoS2 doped with alkaline earth metals (Be/Mg/Ca/Sr/Ba) are systematically studied based on first principles. The results indicate that all the doped systems have a great potential to be formed and structurally stable. In comparison to monolayer MoS2, doping alkaline earth metals results in lattice distortions in the doped system. Therefore, the recombination of photogenerated hole–electron pairs is suppressed effectively. Simultaneously, the introduction of dopants reduces the band gap of the systems while creating impurity levels. Hence, the likelihood of electron transfer from the valence to the conduction band is enhanced, which means a reduction in the energy required for such a transfer. Moreover, doping monolayer MoS2 with alkaline earth metals increases the static dielectric constant and enhances its polarizability. Notably, the Sr–MoS2 system exhibits the highest value of static permittivity, demonstrating the strongest polarization capability. The doped systems exhibit a red-shifted absorption spectrum in the low-energy region. Consequently, the Be/Mg/Ca–MoS2 systems demonstrate superior visible absorption properties and a favorable band gap, indicating their potential as photo-catalysts for water splitting. [ABSTRACT FROM AUTHOR]

Fluorescence imaging in the second near‐infrared II (NIR‐II) window is opening up new possibilities in bioimaging due to its low scattering rate within the tissue. The integration of 2D materials with NIR‐II fluorescence will enable the development of multifunctional imaging probes. However, there are very few 2D materials that can fluoresce in the NIR‐II range. Monolayer WSe2 is a potential 2D material, but its photoluminescence (PL) around 790 nm is still far from the NIR‐II range due to its bandgap of 1.54 eV. In this study, it is investigated the electronic structures, dielectric functions, and PL spectra for Te, I, and Cr‐doped monolayer WSe2, as well as W and S vacant monolayer WSe2. Most of the defected monolayer WSe2 remain semiconductors, except for a few configurations exhibiting metallic properties after making vacancies. Among the monolayer WSe2 under investigation, the Cr‐doped WSe2 performs the best, exhibiting a strong PL peak in NIR‐II with a decreased bandgap around 1.0 eV. As increasing Cr concentration, the peak shifts further toward the red end of the spectrum due to an enhancement of p–d transition. The results provide a useful guideline for material synthesis applied in NIR‐II bioimaging and other biophysics. [ABSTRACT FROM AUTHOR]

Based on density functional theory (DFT), theoretical models of three kinds of lanthanide rare earth metal ion-doped γ-Bi2MoO6 were constructed (Ln-BMO (Ln=Gd, Ho, Yb)). The geometric structure, electronic structure, and optical properties of the model were calculated, and the influence of doped Ln3+ ions on the structures and properties of the system was analyzed. The results revealed that the substitution of smaller ionic radius Ln3+ ions for Bi3+ ions caused a contraction of the lattice parameters. At the same time, the contribution of the [Ln]4d near valence band and conduction band reduced the bandwidth of γ-Bi2MoO6, forming the Ln-O ionic bond with different strengths to obtain higher charge conductivity and charge-separation ability. Secondly, Ln3+ ions have a strongly ionic charge, which leads to the appearance of optical absorption bands in the infrared region and part of the visible region. This reduces the reflection in the visible region, improves the utilization rate, delays the loss of electron energy, and promotes phase matching in the visible region. And the Gd3+-doped system has better photocatalytic activity than the other Ln3+-doped system. This research provides theoretical insights into doped lanthanide rare earth ions and also provides strategies for the modification of γ-Bi2MoO6 nanomaterials. [ABSTRACT FROM AUTHOR]

We present an ab initio calculation to understand electronic structures and optical properties of a tungsten carbide WC being a major component of a TiCN-based cermet. The TiCN-based cermet is widely used as a cutting tool, and is discarded as usual after use. On the other hand, cermet itself is also a famous ingredient of a solar absorption film. We found that the WC has a fairly low-energy plasma excitation ∼ 0.6 eV (2 μ m) and therefore can be a good constituent of a solar selective absorber. The evaluated figure of merit for photothermal conversion is prominently high compared to those of the other materials included in the TiCN-based cermet. The imaginary part of the dielectric function is considerably small around the zero point of the real part of the dielectric function, corresponding to the plasma excitation energy. Therefore, a clear plasma edge appeared, ensuring the high performance of the WC as the solar absorber. This is a fascinating aspect, because the wasted TiCN-based cermet cutting tool can be recycled as the solar absorption film after proper treatments and modifications. [ABSTRACT FROM AUTHOR]

Based on the density functional theory, the effect of rare-earth La doping at different concentrations on the electronic structure, optical properties, and magnetic properties of ZnO was calculated by using the GGA+U method under the condition of spin polarization. The calculation results show that the cell of a La-doped ZnO system is distorted, resulting in a formation energy less than zero, in which case it is easy to dope. After La doping, the band gap narrows, the Fermi level enters the conduction band, and the excess carriers induced by La atoms degenerate to form n-type degenerate semiconductor materials. In the visible light region, a blue shift in the optical absorption edge of the La-doped ZnO system causes an increased average static dielectric constant, stronger polarization ability, stronger binding ability on charges, and the photoconductivity of the doped ZnO system is improved. The magnetic moment of the La-doped ZnO system is zero, so it is not magnetic. [ABSTRACT FROM AUTHOR]

This paper investigated the structural, optical, electronic and thermal characteristics of SrSnO3 perovskites that were calculated using the density functional theory. Software called WEIN2K is used to perform the calculation. According to our calculations, the band gap energy of the SrSnO3 is roughly 4.00 eV and it adopts a distorted cubic shape in the space group Pm3-m. The band structure and partial density of state reflects the major contribution of O 2p in the valence band while 5s orbital from Sn in the conduction band. The electron density plot significantly shows the contribution different clusters SrO12 and SnO6 that plays crucial role in electronic and optical properties. The creation of covalent bonds between the atoms of Sn and O as well as the ionic interaction between the atoms of Sr and O are both demonstrated by the electron density graphs and SCF calculation. The refractive index and extinction coefficient directly correlated with the real and imaginary part of complex dielectric function. Real part of dielectric function shows higher values at two major point of energy 3.54 eV and 9.78 eV associated with the absorption and optical activity of SrSnO3. Negative part of imaginary dielectric function part suggests metallic behavior also supported by -grep lapw method. Thermoelectric and thermal conductivity properties suggest the power factor need to be improved for the device application.

First-principles calculations were used to simulate the aggregation of the peroxy chain defect POL and the oxygen vacancy defect ODC(I). Defect aggregation's electronic structure and optical properties were investigated. The two defects were most likely to accumulate on a 6-membered ring in ortho-position. When the two defects are aggregated, it is discovered that 0.75 ev absorption peaks appear in the near-infrared band, which may be brought on by the addition of oxygen vacancy defect ODC(I). We can draw the conclusion that the absorption peak of the aggregation defect of ODC(I) defect and POL is more prominent in the near infrared region and visible light area than ODC(I) defect and POL defect. [ABSTRACT FROM AUTHOR]

The electronic structures and optical properties of cubic C3N4 doped by vanadium (V) were investigated by first principles. The calculation results of the electronic structure show that V-doped cubic C3N4 can produce two intermediate bands around the Fermi level. The calculation results of the optical properties show that V doping can significantly increase the light absorption of cubic C3N4 in UV–visible region. Therefore, the overall calculated results show that V-doped cubic C3N4 can produce new intermediate band structures and improve the optical performance of the material. [ABSTRACT FROM AUTHOR]