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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]

The monoclinic semiconductor GeP is a new class of Group IV–V layered material, and it shows attractive anisotropic optical and electronic properties. In this paper, we investigate the structural and electronic evolution of layered GeP under pressure, using in situ x-ray diffraction, Raman and infrared spectra, and the density functional theory. All characterization methods reveal that the pressure causes two obvious phase changes. One isostructural transition is observed around 6 GPa. Above 21 GPa, another crystalline-to-amorphous transformation is obtained. It is worth noting that the high-pressure amorphous state can be retained at ambient conditions after the pressure is released. In addition, the pressure-induced red-shift of absorbance edge suggests its bandgap decreases with pressure. This result indicates that pressure has a significant effect on GeP. Meanwhile, it also provides a method for obtaining amorphous GeP, which is of interest to the energy storage community as it is a potential anode material for lithium-ion batteries. [ABSTRACT FROM AUTHOR]

The optical properties of TiO2 are changed while doped with impurity atoms. This paper made a systematical calculation of the bandgap, the density-of-states (DOS), the optical properties for pure TiO2, and Bi-doped anatase TiO2 according to the first-principles plane wave ultrasoft pseudopotential method which is primarily based on the density functional theory (DFT). The calculation results exhibit that the bandgap decreased after doping, and the impurity energy level is produced into the bandgap of Bi-doped TiO2, which makes red-shift for the absorption band edge of Bi-doped TiO2 and the absorption is enhanced more in the visible light range. [ABSTRACT FROM AUTHOR]

The optical properties of TiO2 are changed while doped with impurity atoms. This paper made a systematical calculation of the bandgap, the density-of-states (DOS), the optical properties for pure TiO2, and Bi-doped anatase TiO2 according to the first-principles plane wave ultrasoft pseudopotential method which is primarily based on the density functional theory (DFT). The calculation results exhibit that the bandgap decreased after doping, and the impurity energy level is produced into the bandgap of Bi-doped TiO2, which makes red-shift for the absorption band edge of Bi-doped TiO2 and the absorption is enhanced more in the visible light range. [ABSTRACT FROM AUTHOR]

Summary: In this paper, we present the first principle investigations for structural and optoelectronic properties of pure, n‐type, p‐type, and co‐doped MgSiP2 chalcopyrite compounds. To examine the structural and optoelectronic response, density functional theory (DFT) as embodied in Wien2k method is utilized. Within DFT, we have considered the exchange correlation functional prescribed by Perdew‐Burke‐Ernerhof generalized gradient approximation and Tran‐Blaha modified Becke Johnson for all computation presented in this paper. The results obtained from present calculations are in well reconciliation with previously reported experimental and theoretical data for pure compound, which affirms the accuracy of present computations. The electronic responses of all compounds are investigated through the crystal structure, energy band structure, and density of states. Optical responses of studied compounds are explained in terms of dielectric tensor, absorption, reflectivity, and refractivity spectra. Drastic change in energy band gap from pure (2.04 eV) to co‐doped compound (0.30 eV) is observed. The obtained band gaps and absorption range confirm the utility of these compounds in photovoltaic application. [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]

Summary: In this paper, we present the first principle investigations for structural and optoelectronic properties of pure, n‐type, p‐type, and co‐doped MgSiP2 chalcopyrite compounds. To examine the structural and optoelectronic response, density functional theory (DFT) as embodied in Wien2k method is utilized. Within DFT, we have considered the exchange correlation functional prescribed by Perdew‐Burke‐Ernerhof generalized gradient approximation and Tran‐Blaha modified Becke Johnson for all computation presented in this paper. The results obtained from present calculations are in well reconciliation with previously reported experimental and theoretical data for pure compound, which affirms the accuracy of present computations. The electronic responses of all compounds are investigated through the crystal structure, energy band structure, and density of states. Optical responses of studied compounds are explained in terms of dielectric tensor, absorption, reflectivity, and refractivity spectra. Drastic change in energy band gap from pure (2.04 eV) to co‐doped compound (0.30 eV) is observed. The obtained band gaps and absorption range confirm the utility of these compounds in photovoltaic application. [ABSTRACT FROM AUTHOR]

With the development of industrialization, the use of mercury in industry has become more and more widespread, causing serious impacts on the environment. It is therefore urgent to find new effective ways to combat mercury pollution. In this paper, The effect of C, O, P, Ni and Au doping on the adsorption of Hg atoms by WS 2 has been investigated based on the first nature principle of density functional theory. The electronic structures and optical properties of the adsorbed systems were calculated after atomic doping. The results show that the absolute value of the adsorption energy of the intrinsic adsorption system is small and does not favour the adsorption of Hg on WS 2. However, after C, P, Ni and Au doping, the adsorption energy of the system is significantly increased and a strong charge transfer between WS 2 and Hg atoms occurs, as well as a significant change in the band gap of the structure. This suggests that atomic doping favors the adsorption of Hg by WS 2. The effect of O doping on the adsorption system is not significant. In addition, a study of the optical properties revealed that the static dielectric constants of the system appeared to increase to varying degrees after the doping of the atoms. The doping of P, Ni and Au atoms increases the light absorption coefficient and contributes to the photocatalytic efficiency of the structures. The doped atoms cause a red shift in the reflectivity peak of the adsorbed system. In summary, the doping of C, P, Ni and Au enhances the adsorption of Hg atoms on WS 2. O doping has less effect on the adsorption of Hg on WS 2. • In this paper, the effect of C, O, P, Ni and Au doping on the adsorption of Hg atoms by WS2 was investigated. • The results show that atomic doping favors the adsorption of Hg by WS2. • Atomic doping alters the electronic properties of the structure. • Atomic doping alters the optical properties of the structure. [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]

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 effects of bend angle on the stability, electronic structure and optical properties of Li-absorbed borophene system are studied by using density functional theory based on the first principles. The structure of borophene did not change significantly after adsorption of a Li atom, and the planar structure of borophene was not destroyed. Bending deformation affects the stability of the adsorption system and reduces the binding energy of the adsorption system. The adsorption of Li atoms obviously changes the energy band structure of borophene, and more impurity levels appear in the conduction band. The 2s orbital of Li and the 3p orbital of B are obviously hybridised. A charge transfer occurs between Li atoms and borophene. As the deformation increases, the amount of charge transfer increases. The bending angle affects the size of the absorption peak and reflection peak of the adsorption system. [ABSTRACT FROM AUTHOR]

Two-dimensional stanene is limited in its application in nanoscale optoelectronic devices due to its zero-bandgap. Based on first-principles calculations of density functional theory, the effects of adsorption of Be atoms with different coverages and torsional deformation on the structure, electricity, and optics of stanene are systematically investigated. The adsorption of Be atoms makes stanene have an adjustable bandgap, the surface state is successfully transformed from a zero-bandgap quasi-metal to a semiconductor with a maximum bandgap of 0.260 eV, the change in Be atom coverage causes a blueshift of the absorption and reflection peaks. Torsional deformation can effectively adjust the bandgap of stanene, which varies from 0.278 eV to 0.110 eV. Torsion enhances the maximum absorption peak of light. Stanene is expected to be a candidate material for designing new nanoelectronic devices. [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]

Functionalized MXenes have attracted great interest due to their unique electrical, magnetic, optical, and electrochemical properties. In this paper, the effect of interlayer coupling on the electronic structures of Ti 2 CO 2 MXenes is investigated by using density functional theory. Due to the interlayer coupling, the band structures of Ti 2 CO 2 nanosheet are split, generating an indirect band gap of 0.869 eV, which is smaller than that of Ti 2 CO 2 monolayer (1.044 eV). Biaxial strain can be used to achieve the transitions of direct-indirect-negative band gaps semiconductor. The interlayer interaction effectively inhibits the structural changes under stress, resulting that the band gap of nanosheet be adjusted in a large stress range. Furthermore, the change trend of imaginary part ε 2 of the dielectric function indicates that stress has an obvious regulatory effect on the optical transition. The different responses of monolayer and nanosheet under stress provides more choice for the optical devices of Ti 2 CO 2 MXenes. [ABSTRACT FROM AUTHOR]

Context: The monoclinic L-histidine crystal is critical for protein structure and function and is also found in the myelin of brain nerve cells. This study numerically examines its structural, electronic, and optical properties. Our findings indicate that the L-histidine crystal has an insulating band gap of approximately 4.38 eV. Additionally, electron and hole effective masses range between 3.92 m 0 –15.33 m 0 and 4.16 m 0 –7.53 m 0 , respectively. Furthermore, our investigation suggests that the L-histidine crystal is an excellent UV collector due to its strong optical absorption activity for photon energies exceeding 3.5 eV. Methods: To investigate the structural, electronic, and optical properties of L-histidine crystals, we used the Biovia Materials Studio software to conduct Density Functional Theory (DFT) simulations as implemented in the CASTEP code. Our DFT calculations were performed using the generalized gradient approximation (GGA) as parameterized by the Perdew-Burke-Ernzerhof (PBE) exchange-correlation functional, with an additional dispersion energy correction (PBE + TS) based on the model proposed by Tkatchenko and Scheffler to describe van der Waals interactions. Additionally, we employed the norm-conserving pseudopotential to treat core electrons. [ABSTRACT FROM AUTHOR]

Series of new inorganic–organic hybrid hexamolybdate‐julolidine materials are theoretically designed and studied via density functional theory (DFT) and time‐dependent density functional theory (TD‐DFT). Their geometric and electronic structures, linear optical and second‐order nonlinear properties have also been evaluated. By the introduction of julolidine into the organoimido‐hexamolybdate, the studied systems show substantial second‐order nonlinear (NLO) responses of up to 1048 × 10−30 esu for compound 3. Upon enlarging the π‐conjugated linker, the calculated β‐responses are enhanced by a factor of 2.1. In addition, TD‐DFT calculations indicate that the strong low‐energy transition can mainly be attributed to charge transfer (CT) from julolidine‐arylimido to the hexamolybdate cluster, indicating strong communication between the POM and julolidine components, which is responsible for the linear and non‐linear optical behavior of these compounds. Ortho‐methylation to the imido‐bond has a significant effect on the stability and hence the length and linearity of the bond, although it slightly reduces the first hyperpolarizability. The whole set of results demonstrates the excellent NLO activity for julolidine‐POMs chromophores while keeping relatively good transparency window compared to similar purely organic systems. [ABSTRACT FROM AUTHOR]

Based on density functional theory, the electronic and optical properties of double perovskites Ba2MnWO6 were studied using the generalized gradient approximation. We have looked into four magnetic configurations, such as collinear antiferromagnetic AF-1, AF-2 and noncollinear antiferromagnetic AF-NC1, AF-NC2 structures. The obtained results show that the valence band maximum is mainly dominated by Mn-3d orbitals, while the conduction band minimum is mainly composed of W-5d orbitals. In addition, Ba2MnWO6 is shown as an indirect band gap semiconductor. The gap between two main t2g,↑ and e2g,↑ manifolds of Mn-3d states, located at about 1.9 and 1 eV below Fermi level, is initiated as consequence of splitting in crystal field. From calculated optical results, Ba2MnWO6 indicates excellent light absorption in the ultraviolet range. Consequently, this material promises potential optical applications, such as solar cell functional in ultraviolet light. [ABSTRACT FROM AUTHOR]

In this paper, the effects of Al doping and equibiaxial strain on monolayer h-BN were investigated by first-principles calculations. The results show that with tensile strain applied, the structure of the material is more stable, while the structural stability of the material decreases when compressive strain is applied. When the monolayer h-BN is doped with Al, the band gap decreases, and the higher the doped Al concentration, the lower the band gap. Equibiaxial strain is very effective for band gap tuning of monolayer h-BN. The optical calculation results show that the peaks of dielectric function and optical constant of the material decrease after Al doping, and the peaks decrease with the increase of Al concentration. When the strain is tensile, the optical properties of the material will be red-shifted as a whole, and the optical properties of the material will be blue-shifted when compressive strain is applied. After the monolayer h-BN was doped with two Al atoms and a strain of −9% was applied, the optical properties of the material were significantly affected. Our study provides some theoretical implications for the application of monolayer h-BN in the field of spintronic devices and optoelectronic devices. • The effect of equbiaxial strain and Al doping on monolayer h-BN were investigated. • Using first principles based on density functional theory. • Compared with the compression strain, the structure of the material is more stable under the tensile strain. • Band gap decreases with increasing Al doping concentration. • Optical properties of the material are red-shifted with tensile strain and blue-shifted with compressive strain. [ABSTRACT FROM AUTHOR]

In this paper, the structural, elastic, electronic and optical properties of double-perovskite halides Rb 2 CuBiX 6 are studied using first-principles calculations based on density functional theory. The results show that Rb 2 CuBiX 6 (X = Br, Cl) have thermodynamic and mechanical stability according to the tolerance factor, binding energy, formation energy and Born-Huang stability criterion. The B/G value and Poisson's ratio indicate that Rb 2 CuBiX 6 is a flexible material. Rb 2 CuBiBr 6 and Rb 2 CuBiCl 6 are indirect bandgap semiconductors with bandgap values of 1.11 eV and 1.43 eV, respectively. In addition, the effective masses of electrons of Rb 2 CuBiX 6 are much smaller than that of other perovskite compounds, indicating that they have better carrier mobility. In the visible light range, Rb 2 CuBiX 6 has good dielectric properties and excellent light absorption properties. Therefore, Rb 2 CuBiX 6 has great potential in photovoltaic application due to their suitable bandgap values and excellent optical properties. • The bandgap values of Rb 2 CuBiX 6 (X = Br, Cl) are very suitable for photosensitive materials of solar cells. • The Rb 2 CuBiX 6 can be a potential candidate for excellent light absorbing material. • Rb 2 CuBiX 6 is the structural and thermodynamic stabilities. [ABSTRACT FROM AUTHOR]

Pyrophosphate crystals have a wide array of applications in industrial and biomedical fields. However, fundamental understanding of their electronic structure, optical, and mechanical properties is still scattered and incomplete. In the present research, we report a comprehensive theoretical investigation of 21 pyrophosphates A2M (H2P2O7)2•2H2O with either triclinic or orthorhombic crystal structure. The molecule H2P2O7 is the dominant molecular unit, whereas A = (K, Rb, NH4, Tl), M = (Zn, Cu, Mg, Ni, Co, Mn), and H2O stand for the cation elements, transition metals, and the water molecules, respectively. The electronic structure, interatomic bonding, partial charge distribution, optical properties, and mechanical properties are investigated by first-principles calculations based on density functional theory (DFT). Most of these 21 crystals are theoretically investigated for the first time. The calculated results show a complex interplay between A, M, H2P2O7, and H2O, resulting in either metallic, half-metallic, or semi-conducting characteristics. The novel concept of total bond order density (TBOD) is used as a single quantum mechanical metric to characterize the internal cohesion of these crystals to correlate with the calculated properties, especially the mechanical properties. This work provides a large database for pyrophosphate crystals and a road map for potential applications of a wider variety of phosphates. [ABSTRACT FROM AUTHOR]

Based on the density functional theory (DFT) as incorporated in the Wien2k package, the lattice parameters and atomic position of calcium niobate (CaNb2O6) were optimized. Furthermore, the electronic, optical, and structural properties of the relaxed compound were calculated. Relaxed calcium niobate presents a direct band gap with 3.5 eV, which makes it a good candidate for photovoltaic applications. The DFT calculation reveals that the O atoms make the major contributions in the valence band, while Nb and Ca atoms are the dominant contributors in lower and upper portions of the conduction band, respectively. Moreover, the optical properties of compounds such as refractivity, dielectric constant, reflectivity, etc. are calculated and discussed in detail. [ABSTRACT FROM AUTHOR]

The Janus two-dimensional (2D) materials have recently demonstrated excellent physical and chemical properties. The electronic, thermoelectric, and optical properties of the Janus In2SeTe monolayer have been investigated using density functional theory (DFT) calculations. Our results revealed the Janus In2SeTe monolayer has a direct bandgap of 1.07 eV, which is desirable and smaller than that of InSe and InTe. The studied optical properties indicate that Janus In2SeTe monolayer has a very good absorbing capability of light from the infrared region to ultraviolet one with a large absorption coefficient. Moreover, the thermoelectric property calculations suggest that the In2SeTe Janus monolayer can be a potential thermoelectric material, with a great electronic figure of merit ( ZT e ) of 0.97 at 300 K. In addition, the ZT e increases with temperature up to a value of 1.42 at 800 K. Our results revealed the Janus In2SeTe monolayer possesses good properties that could offer the possibility of optoelectronic and energy conversion applications. [ABSTRACT FROM AUTHOR]

In this paper, crystal structures, effective masses, electronic and optical properties of B 6 Ch (Ch = O, S, Se, Te) are studied within density functional theory (DFT). The band structures show that B 6 O, B 6 S and B 6 Se are semiconductors, while the zero-bandgap B 6 Te displays metallic properties. Moreover, the optical properties involving absorption coefficients, refractive index and extinction coefficients of B 6 Ch are shown and analyzed. The obtained results lead to a conclusion that B 6 Ch results in heavier effective masses and poor transparency. This is explained by the fact that the s orbitals of anion will cause lower dispersion of band edge and influence its positions. • Explore that B 6 O, B 6 S and B 6 Se are p-type TCO while B 6 Te is metal. • Offer evidence that chalcogen substitution narrow the band gaps of B 6 Ch. • Discover the dispersion of the top of the valence band affects its band edge position. [ABSTRACT FROM AUTHOR]