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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]

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]

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]