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Direct printing nanoparticle-based conductive inks onto paper substrates has encountered difficulties e.g. the nanoparticles are prone to penetrate into the pores of the paper and become partially segmented, and the necessary low-temperature-sintering process is harmful to the dimension-stability of paper. Here we prototyped the paper-based circuit substrate in combination with printed thermoplastic electrically conductive adhesives (ECA), which takes the advantage of the capillarity of paper and thus both the conductivity and mechanical robustness of the printed circuits were drastically improved without sintering process. For instance, the electrical resistivity of the ECA specimen on a pulp paper (6 × 10-5Ω·cm, with 50 wt% loading of Ag) was only 14% of that on PET film than that on PET film. This improvement has been found directly related to the sizing degree of paper, in agreement with the effective medium approximation simulation results in this work. The thermoplastic nature also enables excellent mechanical strength of the printed ECA to resist repeated folding. Considering the generality of the process and the wide acceptance of ECA technique in the modern electronic packages, this method may find vast applications in e.g. circuit boards, capacitive touch pads, and radio frequency identification antennas, which have been prototyped in the manuscript. [ABSTRACT FROM AUTHOR]

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: This study explores, for the first time, using first principles, the impact of substitutional doping with boron (B), carbon (C), and nitrogen (N) on the adsorption of chromium (Cr) on monolayer MoS2. The effects of doping on the Cr adsorption behavior of MoS2 were investigated using four MoS2 systems, namely, pure, boron (B)-doped, carbon (C)-doped, and nitrogen (N)-doped, in order to gain an in-depth understanding of the mechanism of the effects of doping on the electronic structure and optical properties of Cr adsorbed by MoS2, to optimize the properties of MoS2, to explore new areas of application, and to promote the development of materials science. Four MoS2 adsorption systems of Cr adsorption on pure, B-doped, C-doped, and N-doped MoS2 were optimized, and the optimized results showed that the stable adsorption location of Cr on both pure and doped MoS2 was the hollow location at the top of the folded hexagon. The findings reveal that pure MoS2 has an adsorption effect on Cr, and doped elements B, C, and N can promote the adsorption of Cr on MoS2, and the strong and weak order of this promotion is B > C > N. Methods: In this paper, we use the CASTEP module in the simulation software Materials Studio to perform simulation calculations and analyses to optimize the simulation of Cr adsorption by MoS2 doped with B, C, and N atoms using the generalized gradient approximation (GGA) plane-wave pseudo-potential method (Perdew et al. Phys Rev Lett 77(18):3865–3968, 1996), as well as Perdew-Burke-Ernzerhof (PBE) generalized functionals (Segall et al. J Phys: Condens Matter 14(11):2717–2744, 2022). The convergence test reveals that it is more reasonable to set the K-point network to 3 × 3 × 1 and the truncation energy to 400 eV. In this paper, a 3 × 3 × 1 supercell structure with 18 S atoms and 9 Mo atoms is selected. The convergence value of the iteration accuracy is 1.0e − 5eV/atom, and all the atomic forces are less than 0.02eV/Å. Additionally, to prevent MoS2 interlayer interaction, a vacuum layer with a thickness of 18 Å is set in the C direction. The geometrical optimization of the model is performed first, and then the corresponding adsorption energies of the model and the nature of the electronic structure are analyzed. [ABSTRACT FROM AUTHOR]

Context: This study explores, for the first time, using first principles, the impact of substitutional doping with boron (B), carbon (C), and nitrogen (N) on the adsorption of chromium (Cr) on monolayer MoS2. The effects of doping on the Cr adsorption behavior of MoS2 were investigated using four MoS2 systems, namely, pure, boron (B)-doped, carbon (C)-doped, and nitrogen (N)-doped, in order to gain an in-depth understanding of the mechanism of the effects of doping on the electronic structure and optical properties of Cr adsorbed by MoS2, to optimize the properties of MoS2, to explore new areas of application, and to promote the development of materials science. Four MoS2 adsorption systems of Cr adsorption on pure, B-doped, C-doped, and N-doped MoS2 were optimized, and the optimized results showed that the stable adsorption location of Cr on both pure and doped MoS2 was the hollow location at the top of the folded hexagon. The findings reveal that pure MoS2 has an adsorption effect on Cr, and doped elements B, C, and N can promote the adsorption of Cr on MoS2, and the strong and weak order of this promotion is B > C > N. Methods: In this paper, we use the CASTEP module in the simulation software Materials Studio to perform simulation calculations and analyses to optimize the simulation of Cr adsorption by MoS2 doped with B, C, and N atoms using the generalized gradient approximation (GGA) plane-wave pseudo-potential method (Perdew et al. Phys Rev Lett 77(18):3865–3968, 1996), as well as Perdew-Burke-Ernzerhof (PBE) generalized functionals (Segall et al. J Phys: Condens Matter 14(11):2717–2744, 2022). The convergence test reveals that it is more reasonable to set the K-point network to 3 × 3 × 1 and the truncation energy to 400 eV. In this paper, a 3 × 3 × 1 supercell structure with 18 S atoms and 9 Mo atoms is selected. The convergence value of the iteration accuracy is 1.0e − 5eV/atom, and all the atomic forces are less than 0.02eV/Å. Additionally, to prevent MoS2 interlayer interaction, a vacuum layer with a thickness of 18 Å is set in the C direction. The geometrical optimization of the model is performed first, and then the corresponding adsorption energies of the model and the nature of the electronic structure are analyzed. [ABSTRACT FROM AUTHOR]

Context: 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) is a typical insensitive energetic material. It can be used in explosive formulations, such as PBX-9502 and LX-17-0. TATB is an intriguing and unusual explosive for another reason: it crystallizes into a wide array of planar hydrogen bonds, forming a graphite-like layered structure. Therefore, TATB is one of the important research objects, and its surface structure needs to be deeply understood. In this research work, the electronic and energetic properties of TATB (001) surface are explored. Methods: In this paper, the structural, electronic, energetic properties and impact sensitivity of TATB (001) surface structure at 0 and −3 GPa along with x-axis were calculated in this study using the first-principles calculations. The calculations in this paper are performed in the CASTEP code, which is based on the density functional theory with the first-principles calculation method using the plan-wave pseudopotential approach. The exchange-correlation interaction was adopted by the generalized gradient approximation (GGA) with the Perdew-Burke-Ernzerhof (PBE) functional. The DFT-D method with the Grimme correction accurately models van der Waals interactions. To model the surface structures of TATB, the planar slab method was employed. We constructed TATB (001) periodic slabs including three layers with a 15-Å vacuum layer. [ABSTRACT FROM AUTHOR]

Context: The Adenine-based nanotube is theoretically designed, and its transmission spectra are investigated. The quantum-confined Adenine nanotube shows electronic transmission of the carrier at minimum stress. In this paper, the prediction of transmission spectra of the quantum-confined bio-molecular nanotube is investigated and deeply studied. Molecular level structure prediction and their electronic characterization can be possible with ab initio accuracy using a machine learning algorithmic approach. At the molecular level, it is difficult to predict quantum transmission spectra as these results are always hampered by the carrier backscattering effect. However, mostly these predictive models are available for intrinsic semi-conducting materials and other inorganic structures. Methods: Machine learning algorithms are designed to predict the electronic properties of the nano-scale structure. This task is even more difficult when quantum-confined molecular arrangements are considered, whose transmission spectra are sensitive to the confinements applied. This paper presents an effective machine learning algorithms framework for predicting transmission spectra of quantum-confined nanotubes from their geometries. In this paper, we consider regression machine learning algorithms to find maximum accuracy with varying configurations and geometries to excerpt their atoms' local environment information. The Hamiltonian components are then used to enable the utilization of the information to predict the electronic structure at any arbitrary sampling point or k-point. The theoretical basics introduced in this process help to capture and incorporate minor changes in quantum confinements into transmission spectra and provide the framework algorithm with more accuracy. This paper shows the ability to predict the accurate algorithmic models of the Adenine nanotube. In this framework, we have considered a tiny data set to achieve a rapid and reliable method for electronic structure determination and also propose the best algorithm for predictive model analysis. [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]

To test electric devices such as household appliances, electric vehicle and other loads, there is need for emulators instead of real devices, which decreases the cost of testing. This paper presents a dynamically programmable load emulator that imitates the current–time characteristic of different types of the loads. The exact mathematical model of various types of electric loads is firstly extracted. These mathematical models are implemented by LabVIEW software. A non-ideal buck converter is used for the hardware part of the emulator, which is controlled by LabVIEW. The proposed emulator can mimic the types of loads given by LabVIEW software with great accuracy and is an example of an actual load simulator with good approximation. Manufacturers or laboratories of electric equipment can use the proposed emulator to perform their tests instead of using the actual device. This reduces the cost of tests and speeds them up so that all types of electric loads can be modeled with an emulator. In addition, because a simple power electronic converter structure is used, the proposed emulator has low complexity and low manufacturing cost. Simulation and laboratory results prove the efficiency of this emulator in making models of different types of loads. [ABSTRACT FROM AUTHOR]

Context: This research paper investigates the properties and potential applications of antiperovskite materials. Antiperovskites are a class of materials with a unique crystal structure, where the central atom is surrounded by a cage of anions. We review recent research on antiperovskite-based materials for energy storage, photovoltaics, catalysis, and sensors. We discovered that these materials display direct band gap semiconductors, strong absorption in the visible (VIS), ultra-violet (UV), and near infrared regions (NIR) based on their fundamental features, which is the most admirable quality that may be found in many optoelectronic devices. Both mechanical and thermodynamic stability have been confirmed for these materials. We discovered that these materials exhibit high figures of merit through the calculation of transport properties, which makes them a promising candidate for thermoelectric devices. It is anticipated that the proposed material BiPMg3, which has a theoretical efficiency of 11.5%, will make a suitable photovoltaic absorber. This paper highlights the potential of these materials for future technological advancements. Methods: Herein, we have used most authentic techniques to compute fundamental physical properties of these antiperovskites. Full-potential linear augmented plane wave (FP-LAPW) method has been used to investigate electronic, magnetic, optical properties, and make antiperovskites attractive for a variety of applications. In light of its implementation, we have checked the theoretical power conversion efficiency by first principles spectroscopic screening methodology, and inspect the fundamental physical parameters of antiperovskites, focusing on their potential as functional materials for energy and information technologies. [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]

Recent research has demonstrated that the CuFeTe2 compound has interesting physical properties. However, less research effort has been afforded to the study of the stable non-stoichiometric Cu1.1Fe1.2Te2 structure and electronic properties. In this paper, we report the synthesis and electronic properties of the non-stoichiometric (Cu, Fe) co-doped CuFeTe2 (Cu1.1Fe1.2Te2) with a stable single phase. The temperature-dependent resistance and magnetic susceptibility measurements showed an obvious phase transition from a semiconductor to metal when the temperature reached 360 K, revealing a spin-density-wave (SDW)-like state existing in the as-grown Cu1.1Fe1.2Te2, which has a higher SDW transition temperature than that of CuFeTe2. Interestingly, a spectral weight evolution of the angle-resolved photoemission spectroscopy in the study of the electronic structure of Cu1.1Fe1.2Te2 is observed at the same temperature of 360 K. Our work provides a scheme for exploration of novel physical phenomena related to SDW in two-dimensional materials. [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]

Context: In this paper, the structural stability, electronic structure, and optical properties of monolayer MoSe2 doped with C, O, Si, S, and Te atoms, respectively, under defective conditions are investigated based on first principles. It is found that the system is more structurally stable when defecting a single Se atom as compared to defecting a single Mo or two Se atoms. The electronic structure analysis of the system reveals that intrinsic MoSe2 is a direct bandgap semiconductor. The bandgap value of the system decreases with a single Se atom defect and introduces two new impurity energy levels in the conduction band. The defective systems doped with C and Si atoms all exhibit P-type doping. The total density of states of intrinsic MoSe2 is mainly contributed by the Mo-d and Se-p orbitals, and new density of state peaks appears near the conduction band after the defects of Se atoms. The total density of states of the defective system doped by each atom is mainly contributed by Mo-d, Se-p, and the result of the p orbital contribution of each dopant atom. By analyzing the dielectric function of each system, it is found that the intrinsic MoSe2 has the lowest static permittivity and the C-doped defect system has the highest static permittivity, which reaches 21.42. The C- and Si-doped defect systems are the first to start absorbing the light, and the intrinsic MoSe2 absorbs the light later, with its absorption edge starting at 1.25 eV. In the visible range, the reflection peaks of the systems move toward the high-energy region and the blue-shift phenomenon occurs. It is hoped that applying modification means to modulate the physical properties of the two-dimensional materials will provide some theoretical basis for broadening the application of monolayer MoSe2 in the field of optoelectronic devices. Methods: This study utilizes the first principle computational software package MS8.0 (Materials studio8.0) under density functional theory (DFT). The exchange–correlation potential (GGA-PBE) is described by the Perdew-Burke-Ernzerhof correlation function in CASTEP, and the potential function adopts the ultrasoft pseudopotential in the inverse space formulation. The plane wave truncation energy Ecut is set to 400 eV, the K-point is taken as 5 × 5 × 1, and the force convergence criterion is 0.05 eV/Å. The convergence accuracy of the total energy of the system is less than 1.0 × 10−5 eV/atom, the tolerance shift is less than 0.002 Å, and the stress deviation is less than 0.1 GPa. The vacuum layer is taken as 15 Å, which is intended to minimize the interlayer force. The vacuum layer was set to 15 Å to avoid the effect of layer-to-layer interaction forces in the crystal cell. [ABSTRACT FROM AUTHOR]

Context: In this paper, the structural stability, electronic structure, and optical properties of monolayer MoSe2 doped with C, O, Si, S, and Te atoms, respectively, under defective conditions are investigated based on first principles. It is found that the system is more structurally stable when defecting a single Se atom as compared to defecting a single Mo or two Se atoms. The electronic structure analysis of the system reveals that intrinsic MoSe2 is a direct bandgap semiconductor. The bandgap value of the system decreases with a single Se atom defect and introduces two new impurity energy levels in the conduction band. The defective systems doped with C and Si atoms all exhibit P-type doping. The total density of states of intrinsic MoSe2 is mainly contributed by the Mo-d and Se-p orbitals, and new density of state peaks appears near the conduction band after the defects of Se atoms. The total density of states of the defective system doped by each atom is mainly contributed by Mo-d, Se-p, and the result of the p orbital contribution of each dopant atom. By analyzing the dielectric function of each system, it is found that the intrinsic MoSe2 has the lowest static permittivity and the C-doped defect system has the highest static permittivity, which reaches 21.42. The C- and Si-doped defect systems are the first to start absorbing the light, and the intrinsic MoSe2 absorbs the light later, with its absorption edge starting at 1.25 eV. In the visible range, the reflection peaks of the systems move toward the high-energy region and the blue-shift phenomenon occurs. It is hoped that applying modification means to modulate the physical properties of the two-dimensional materials will provide some theoretical basis for broadening the application of monolayer MoSe2 in the field of optoelectronic devices. Methods: This study utilizes the first principle computational software package MS8.0 (Materials studio8.0) under density functional theory (DFT). The exchange–correlation potential (GGA-PBE) is described by the Perdew-Burke-Ernzerhof correlation function in CASTEP, and the potential function adopts the ultrasoft pseudopotential in the inverse space formulation. The plane wave truncation energy Ecut is set to 400 eV, the K-point is taken as 5 × 5 × 1, and the force convergence criterion is 0.05 eV/Å. The convergence accuracy of the total energy of the system is less than 1.0 × 10−5 eV/atom, the tolerance shift is less than 0.002 Å, and the stress deviation is less than 0.1 GPa. The vacuum layer is taken as 15 Å, which is intended to minimize the interlayer force. The vacuum layer was set to 15 Å to avoid the effect of layer-to-layer interaction forces in the crystal cell. [ABSTRACT FROM AUTHOR]

Douglas Hartree and Hilleth Thomas were graduate students together at Cambridge University in the mid-1920s. Each developed an important approximation method to calculate the electronic structure of atoms. Each went on to make significant contributions to numerical analysis and to the development of scientific computing. Their early efforts were fused in the mid-1960s with the development of an approach to the many-particle problem in quantum mechanics called density functional theory. This paper discusses the experiences which led Hartree and Thomas to their approximations, outlines the similarities in their subsequent careers, and highlights the essential role their work played in the foundational papers of modern density functional theory. [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]

Context: This paper presents the results of the study of the electronic structure and cationic and excited states of three spiroborate complexes (2-acetylacetonato-1,3,2-benzodioxaborol, its NH- and NMe-derivatives) and three corresponding ligands (acetylacetone, 4-aminopent-3-en-2-one, and 4-methylaminopent-3-en-2-one). Materials based on spiroborates are used in medicine, for example, as a drug carrier. In industry, spiroborate anions are used in ionic liquids and as alternative high performance lubricants. Analysis of experimental and calculated data allowed determining the influence of functional groups on the parameters of the electronic structure and energy of electronic transitions. Compared to acetylacetone and its NH- and NMe-derivatives, the upper filled molecular orbitals of the corresponding spiroborates are stabilized at 0.4–1.7 eV, which is due to the positive charge of the ligand due to the acceptor properties of the dioxyphenylene fragment. Among the studied compounds, when replacing the oxygen atom in the α-position with the NH- or NMe-group, a bathochromic shift of intense bands in the absorption spectra is observed, since the energy intervals between the orbitals of the π3 and π4 ligand are reduced. In addition, in a number of spiroborates, the violation of C2v symmetry when replacing an oxygen atom leads to the appearance of a low-intensity maximum in the long-wave part of the absorption spectrum, due to the π2X → π4 transition. Method: Complexes were studied by photoelectron spectroscopy, absorption spectroscopy, and high-level ab initio quantum chemical computations, including the algebraic diagrammatic construction method for the polarization propagator of the second order (ADC(2)), the outer-valence Green's function (OVGF), the density functional theory (DFT), the time-dependent density functional theory (TDDFT) and the domain-based local pair natural orbital (EOM-DLPNO) methods. X-ray photoelectronic spectra of two spiroborates in the condensed state were measured using a two-chamber high-vacuum system MXPS XP (Omicron, Germany). UV–visible absorption spectra were recorded using a spectrophotometer 2550 (Shimadzu-UV, Japan). The geometry of all studied compounds was optimized by the DFT/B3LYP/Def2-SVP method. The energy of electron levels in the S0 state and the distribution of electron density at each MO were obtained by the DFT/CAMB3LYP/cc-pVDZ method. The energies of excited states were obtained by the TDDFT/CAMB3LYP/cc-pVDZ, ADC(2)/cc-pVDZ and EOM-DLPNO/cc-pVDZ methods. All DFT and TDDFT calculations were carried out in the GAMESS (US) software computing package. ADC(2) calculations of excited states were performed using the Orca 4.0.1 software package. EOM-DLPNO and OVGF calculations were carried out in the Gaussian 16 software package. [ABSTRACT FROM AUTHOR]

As a typical representative of Ga-based III-V compound semiconductor material, the pressure-induced structural phase transition of gallium phosphide (GaP) has received more attention, while the present work explains the electronic structure and photoconductivity properties under high pressure, especially. The paper focuses on the high-pressure electronic structure and photoconductivity properties up to 50.0 GPa in GaP, along with the ZB (zinc-blende structure) to RS (rock salt structure) phase structural transition using enthalpy calculation. The discontinuous thermal expansion coefficient and unit cell volume collapse by 15.0–15.5% are observed at around 39.2 GPa due to reversible structural phase transition under compression and decompression conditions, which is also reflected in the measured discontinuous Hall coefficient and conductivity at approximately 39.0 GPa. The computed semiconductor-to-metal transition is determined to occur at 24.5 GPa by band-gap closure in good agreement with the experimentally determined transition pressure. The light illumination provides a potential way to reduce conductivity without effect on pressure of phase transition. [ABSTRACT FROM AUTHOR]

Based on first-principles calculations using density functional theory, this paper systematically studies the effects of uniaxial tension-compression deformation on the stability and electrical and thermal properties of monolayer graphene and AA stacked bilayer graphene. The study shows that the original symmetry of graphene is broken by the tensile and compression deformations, catalyzing the interlayer coupling of bilayer graphene. Its electronic energy band, phonon dispersion, and other physical properties have changed. The transition from metalloid to semiconductor has completed since the deformation weakens the stability of the graphene system to varying degrees and opens the band gap of monolayer graphene. The band gap becomes larger with the increase of tensile and compressive deformation, in which way it can be adjusted. Influenced by the tiny tensile deformation, metalloid properties are exhibited by a small band gap of intrinsic AA-stacked bilayer graphene, and then the band gap becomes larger as the deformation increases. A band gap appears in the system phonon dispersion curves when the compression deformation increases to −15%. The phonon mode softens and shows virtual frequency. The value of virtual frequency increases with the increase of compression deformation. At the very moment, the vibration mode is discontinuous, and the system is unstable. [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]

In this paper, the effect of substitutional doping of boron (B), carbon (C), nitrogen (N), oxygen (O), and phosphorus (P) at the S-site on the electronic structure of the monolayer TiS2 system is investigated using a first-principles calculation method. The effect of nonmetal doping on the band gap of TiS2 and its mechanism were studied by analyzing the stability, electronic structure, and charge transfer of the system. By calculating the electron cloud overlap population and formation energy, we confirmed that the system is stable, and the Ti–X bond length of the doped system undergoes different degrees of distortion. The properties of the B, C, and N doped system show different properties with different doping concentrations; the band gap of the O-atom system gradually expands with the rise of the doping rate. The hybridization positions of the impurity and the intrinsic atoms are found by comparing the DOS; combined with the charge density difference, we confirmed the interaction of impurity atoms with the system and revealed the bonding process of different systems. [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: Ni-rich layered oxides have been widely studied as cathodes because of their high energy density. However, the gradual structural transformation during the cycle will lead to the capacity degradation and potential decay of the cathode materials. In this paper, first-principle calculations were used to investigate the formation energy, and geometric and electronic structure of Mg-doped LiNiO2 cathode for Li-ion batteries. The results show that Mg doping has little effect on the geometric structure of LiNiO2 but has great effect on its electronic structure. Our data give an insight into the microscopic mechanism of Mg-doped LiNiO2 and provide a theoretical reference for experimental research, which is helpful to the design of safer and higher energy density Ni-rich cathodes. Method: In this work, all calculations were performed by the VASP package; the PBE functional in the generalized gradient approximation (GGA) was employed to describe the exchange–correlation interactions. An energy cutoff of 520 eV and a 5 × 5 × 3 Monkhorst–Pack mesh of k-point sampling in the Brillouin zone were chosen for all calculations. All atoms were relaxed until the convergences of 10−5 eV/f.u in energy and 0.01 eV/Å in force were reached. [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]

Many materials exhibit phase transitions at which both the electronic properties and the crystal structure change. Some authors have argued that the change in electronic order is primary, with the lattice distortion a relatively minor side-effect, and others have argued that the lattice distortions play an essential role in the energetics of the transition. In this paper, we introduce a formalism that resolves this long-standing problem. The methodology works with any electronic structure method that produces solutions of the equation of state determining the electronic order parameter as a function of lattice distortion. We use the formalism to settle the question of the physics of the metal–insulator transitions in the rare-earth perovskite nickelates (RNiO3) and Ruddlesden–Popper calcium ruthenates (Ca2RuO4) in bulk, heterostructure, and epitaxially strained thin film forms, finding that electron-lattice coupling is key to stabilizing the insulating state in both classes of materials. For phase transitions involving concomitant structural and electronic changes, it has been challenging to determine which component provides the dominant contribution. Here, a general formalism capable of resolving this question is introduced and applied to metal–insulator transitions in two material families. [ABSTRACT FROM AUTHOR]

This paper describes the development of mixed B-site pyrochlore Y2MnRuO7 electrocatalyst for oxygen evolution reaction (OER) in acidic media, a challenge for the development of low-temperature electrolyzer for green hydrogen production. Recently, several theories have been developed to understand the reaction mechanism for OER, though there is an uncertainty in most of the cases, due to the complex surface structures. Several key factors such as lattice oxygen, defect, electronic structure, oxidation state, hydroxyl group and conductivity were identified and shown to be important to the OER activity. The contribution of each factor to the performance however is often not well understood, limiting their impact in guiding the design of OER electrocatalysts. In this work, we showed mixed B-site pyrochlore Y2MnRuO7 catalyst exhibits 14 times higher turnover frequency (TOF) than RuO2 while maintaining a low overpotential of ~ 300 mV for the entire testing period of 24 h in acidic electrolyte. X-ray photoelectron spectroscopy (XPS) analysis reveals that this B-site mixed pyrochlore Y2MnRuO7 has a higher oxidation state of Ru than those of Y2Ru2O7, which could be crucial for improving OER performance as the broadened and lowered Ru 4d band resulted from the B-site substitution by Mn is beneficial to the OER kinetics. [ABSTRACT FROM AUTHOR]

The exchange of knowledge across different areas and disciplines plays a key role in the process of knowledge creation, and can stimulate innovation and the emergence of new fields. We develop here a quantitative framework to extract significant dependencies among scientific disciplines and turn them into a time-varying network whose nodes are the different fields, while the weighted links represent the flow of knowledge from one field to another at a given period of time. Drawing on a comprehensive data set on scientific production in modern physics and on the patterns of citations between articles published in the various fields in the last 30 years, we are then able to map, over time, how the ideas developed in a given field in a certain time period have influenced later discoveries in the same field or in other fields. The analysis of knowledge flows internal to each field displays a remarkable variety of temporal behaviours, with some fields of physics showing to be more self-referential than others. The temporal networks of knowledge exchanges across fields reveal cases of one field continuously absorbing knowledge from another field in the entire observed period, pairs of fields mutually influencing each other, but also cases of evolution from absorbing to mutual or even to back-nurture behaviors. [ABSTRACT FROM AUTHOR]

In this paper, we report a theoretical study of the electronic structure of copper oxides. The band structure of the copper oxides Cu2O and CuO has been calculated in the density functional approach by the full-potential linearized augmented plane wave method, using the modified Becke–Johnson (mBJ) potential. The results demonstrate that the use of the modified Becke–Johnson potential ensures better agreement of band structure calculation results for the copper oxides with experimental data then does the generalized gradient approximation (GGA). The use of the mBJ potential allows both compounds to be described as semiconductors whose band structure parameters are in qualitative agreement with experimental data. We have calculated copper L3-edge and oxygen K-edge X-ray absorption near edge structure spectra of Cu2O and CuO at different occupancies of the core level from which an electron transition occurs and compared the calculation results with experimental data. [ABSTRACT FROM AUTHOR]

In this paper, the effect of pressure on the structural stability, elasticity, thermodynamics, and associated electronic structure of L12-type Ni3X (X = Al, Ti, V, Nb) phases is investigated using a first-principles approach. It is shown that pressure leads to volume compression of the Ni3X phase and reduction of the lattice parameters. The increase of pressure promotes the increase of elastic constants, bulk modulus, shear modulus, and Young's modulus. And there is an extremely strong linear correlation between the pressure and the elastic constants. The calculated elastic constants indicate that the pressure leads to strong mechanical stability and ductility of the Ni3X phase. Mechanical anisotropy of the Ni3X phase also increases with increasing pressure. The electronic analysis shows that the increase in pressure leads to enhanced Ni-d-orbitals and X-d-orbitals hybridization and increased electron transfer. The order in terms of electron accumulation intensity is Ni3Ti > Ni3Nb > Ni3V > Ni3Al. It is more directly reflected in the charge density difference diagram. This is in agreement with the results of the enthalpy of formation (ΔH) and Debye temperature (ΘD) analysis. [ABSTRACT FROM AUTHOR]

Abstract—: This paper presents a theoretical study of the effects of crystal structure and Mn and Co substitutions for Cd on the electronic structure of the topological material Cd3As2. We have carried out density functional theory calculations of the band structure and density of states in tetragonal and cubic Cd3As2, as well as in Cd3 -xMnxAs2 and Cd3 -xCoxAs2 crystals. The results indicate that the band structure of the cubic Cd3As2 phase differs significantly from that of a Dirac semimetal, characteristic of the tetragonal phase. It has also been shown that, after Co substitution for 1/24 of the Cd atoms, the structure of the density of 3d electron states is similar to that of the density of states in the magnetic semiconductor Cd3 -xMnxAs2, with a characteristic minimum at the Fermi energy. At the same time, in the case of analogous Mn substitution for Cd, the density of d-electron states has no such minimum. [ABSTRACT FROM AUTHOR]

Research has shown half (Pr0.5Ba0.5MnO3-δ) perovskite to exhibit good electronic and magnetic properties. However, it is necessary to clarify whether electronic transport originates in the cubic or hexagonal phase. This paper explores Ba-doped Pr1-xBaxMnO3-δ (x = 0.35, 0.4, 0.45 and 0.5) disordered perovskites with mixed valence states. The cubic-phase transition increases when the EDTA sol–gel synthesis method was used. Electrical conductivity studies demonstrate that cubic P m 3 ¯ m space group symmetry with a little number of oxygen vacancies enhances conductivity. The origin of this process has been explained in terms of the transition from Mn4+ → Mn3+ ions forming hopping sites for electrons/holes. Rietveld refinement, HRTEM, and XPS confirm a complete structure transition to single cubic perovskite. Charge carrier transport clarifies that the cubic perovskite structure enhances the electrical conductivity more effectively than their cubic/hexagonal mixture counterparts. Our results suggest that the activation energy for electron transport is independent of symmetry but not of Pr3+ concentration. Electrical conductivity increases up to twice as much (182 Scm−1) suggested by previously published research, ratifying its potential application as a cathode for SOFC. [ABSTRACT FROM AUTHOR]

First principles were used to investigate electronic properties of Au-doped graphene, Ag-doped graphene, and Cu-doped graphene and the effect of adsorption behavior of hydrogen sulfide (H2S) molecule on their electronic properties. Doped graphene exhibits interesting electronic properties. The gap value of Ag-doped graphene is 0.29 eV, whereas Au-doped graphene is 0.48 eV which is the largest one in three doped systems, a clear difference of structure and electronic properties among three doped systems absorbing H2S molecule. The doped atom and the H2S molecule are on the same side of the graphene for Au-doped graphene and Cu-doped graphene, which belong to a kind of bonding orbital hybridization of electron cloud showed from charge difference density plots. However, Ag-doped graphene adsorbed with H2S molecule exhibits a kind of antibonding orbital hybridization. With the analysis in this paper, it is beneficial to research H2S gas sensors. [ABSTRACT FROM AUTHOR]

The interface bonding mechanism between Ti3Al0.125Cr0.875 N coating and WC carbide tool is calculated and analyzed based on the first-principles calculations in this paper. The Ti3Al0.125Cr0.875 N(010) (Cr)/WC (100) interface structure is the most stable interface model by calculating the adhesion work, interface energy and fracture toughness of the interface structure. When subjected to external forces, cracks tend to appear in the matrix, which has a certain protection effect on the interface joint. Furthermore, the bonding nature and bonding characteristics at the interface are further explained from the perspective of electronic structure. A new Cr-C bond is formed at the interface, and the bond length is 1.832 nm, which is smaller than other bond lengths in the interface structure, making the interface more stable. It provides theoretical basis for the research of carbide tool interface in future. [ABSTRACT FROM AUTHOR]

Tirapazamine (TP) has been shown to enhance the cytotoxic effects of ionizing radiation in hypoxic cells, thus making it a candidate for a radiosensitizer. This selective behavior is often directly linked to the abundance of O2. In this paper, we study the electronic properties of TP in vacuum, micro-hydrated from one up to three molecules of water and embedded in a continuum of water. We discuss electron affinities, charge distribution, and bond dissociation energies of TP, and find that these properties do not change significantly upon hydration. In agreement with its large electron affinity, and bond breaking triggered by electron attachment requires energies higher than 2.5 eV, ruling out the direct formation of bioactive TP radicals. Our results suggest, therefore, that the selective behavior of TP cannot be explained by a one-electron reduction from a neighboring O2 molecule. Alternatively, we propose that TP's hypoxic selectivity could be a consequence of O2 scavenging hydrogen radicals. [ABSTRACT FROM AUTHOR]

The paper focuses on a low-rank tensor structured representation of Slatertype and Hydrogen-like orbital basis functions that can be used in electronic structure calculations. Standard packages use the Gaussian-type basis functions which allow us to analytically evaluate the necessary integrals. Slater-type and Hydrogen-like orbital functions are physically more appropriate, but they are not analytically integrable. A numerical integration is too expensive when using the standard discretization techniques due the dimensionality of the problem. However, it can be effectively performed using the tensor representation of basis functions. Furthermore, this approach can take advantage of parallel computing. [ABSTRACT FROM AUTHOR]

In this paper, using first-principles calculations based on density function theory, we systematically investigate the electronic structures and properties of the bilayer g-SiC3 systems. Among all three bilayer g-SiC3 systems considered here, the AA stacking (all C/Si atoms in upper SiC3 layer lie above the C/Si atoms in lower SiC3 layer) with an indirect bandgap is most stable. The bandgap calculated by PBE and HSE06 are 1.380 eV and 1.959 eV, respectively. Our results revealed that the bandgap could be modulated effectively by applying in-plane biaxial compressing/stretching or vertical strain along the 'z' axis. When the tensile stress reaches 3%, the bilayer AA g-SiC3 system changes from semiconductor to semimetal. Moreover, under vertical stretching of ∆d = 0.4 Å (d = 2.83 Å), the bilayer AA g-SiC3 turns from an indirect bandgap semiconductor to a direct bandgap semiconductor, which is attractive for realizing the nanoscale multi-functional device applications. Our results provide a theoretical understanding for future SiC3-based electronic nanodevices with controlled bandgaps. [ABSTRACT FROM AUTHOR]

Great progress has been made in O2 adsorption on gold clusters. However, systematic investigations of O2 adsorption on Au 16 − clusters have not been reported. Here, we present a systematic study of the structural, electronic, and adsorptive properties of Au 16 O 2 – clusters by density functional theory (DFT) calculations coupled with stochastic kicking method. Global minimum searches for Au 16 O 2 – reveal that exohedral derivatives are more favored. Furthermore, the obtained ground-state structure exhibits significant stability, as judged by its larger adsorption energy (1.16 eV) and a larger HOMO-LUMO gap (0.57 eV). The simulated photoelectron spectra (PES) of Au 16 O 2 – isomers will be instructive to identify the structures in future experiments. There are three interesting discoveries in the present paper: (1) O2 undergoes chemical adsorption onto the parent Au 16 − clusters, but the amount of the adsorption energy is related to the parent Au 16 − clusters; (2) the process that O2 undergoes dissociative adsorption onto the parent Au 16 − clusters is exothermic; (3) Au 16 O 2 – isomers show smaller X-A energy gaps than those of parent Au 16 − clusters, reflecting that their geometric and electronic structures are distorted remarkably due to dissociative adsorption of O2. [ABSTRACT FROM AUTHOR]

In this paper, Ni2P nanoparticles is incorporated onto the graphene & carbon nanotubes composite (Ni2P NPs/rGO & CNTs) to form flexible free-standing intertwining network film anodes for improving the cycle-life of sodium-ion batteries (SIBs). Benefited from the volume accommodation by this Ni2P NPs/rGO & CNTs structure and its excellent electronic conductive network along with high mechanical strength, such an anode-based SIB shows a superior capacity retention with a stable and long cycle-life at high current densities. For Ni2P NPs/rGO & CNTs electrode, it remains a capacity of 224 mAh g−1 after 100 cycles, at a high current density of 0.5 A g−1, the Ni2P NPs/rGO & CNTs can still maintain a stable reversible capacity of ~ 150 mAh g−1 after 500 cycles, after cycling at a rate as high as 1 A g−1, the reversible capacity of the Ni2P NPs/rGO/CNT can still sustain stable capacities at 91 mAh g−1 after 2000 cycles, respectively. Even at 5 A g−1, it still exhibits a high rate capacity of 65 mAh g−1, thus exhibiting an excellent sodium storage kinetics. [ABSTRACT FROM AUTHOR]

Hydrogen is a clean energy with high efficiency, while the storage and transport problems still prevent its extensive use. Because of the large specific surface area and unique electronic structure, two-dimensional materials have great potential in hydrogen storage. Particularly, monolayer 2H-WS2 has been proven to be suitable for hydrogen storage. But there are few studies concerning the other two phases of WS2 (1T, 1T′) in hydrogen storage. Here, we carried out first-principle calculations to investigate the hydrogen adsorption behaviors of all the three phases of WS2. Multiple hydrogen adsorption studies also evaluate the hydrogen storage abilities of these materials. Comprehensive analysis results show that the 1T′-WS2 has better hydrogen storage performance than the 2H-WS2, which means phase engineering could be an effective way to improve hydrogen storage performance. This paper provides a reference for the further study of hydrogen storage in two-dimensional materials. [ABSTRACT FROM AUTHOR]

α-SiAlON ceramics have been in use as engineering ceramics in the most arduous industrial environments such as molten metal handling, cutting tools, gas turbine engines, extrusion molds, thermocouple sheaths, protective cover for high-temperature sensors, etc., owing to their outstanding mechanical, thermal and chemical stability. Taking advantage of the intrinsic properties of α-SiAlONs, we investigate, in this paper, the possibility of using the Er-doped α-SiAlON (Er-α-SiAlON) ceramic as a high-temperature sensing material via its unique near-infrared to visible upconversion property. We first use neutron diffraction and density functional theory calculations to study the electronic structure and thermodynamic stability of Er-α-SiAlON. It is found that the interstitial doping of Er stabilizes the α-SiAlON structure via chemical bonds with O-atoms with N:O ratio of 5:2 in the seven-fold coordination sites of the Er3+ ion. Temperature-dependent upconversion emissions are then studied under 980 and 793 nm excitations over a temperature range of 298–1373 K and the fluorescence intensity ratio (FIR) technique has been employed to investigate the temperature sensing behavior. Temperature-dependent Raman behavior is also investigated. We demonstrate that using Er-α-SiAlON as a sensing material, the limit of temperature measurement via the FIR technique can be pushed well beyond 1200 K. [ABSTRACT FROM AUTHOR]

Oxide films were formed at 350 °C in borate buffer solution on AISI 304 stainless steel priory abraded with wet SiC paper of different grit size. The films were characterised by Atomic Force Microscopy (AFM) and studied by capacitance, impedance, and photocurrent measurements. The images obtained by AFM microscopy show the evolution of the surface roughness of the films with increasing grit size. Capacitance measurements show that, in all cases, the electronic structure of the films is comparable to that of a p–n heterojunction. This structure is due to the development of space charge layers in the outer iron oxide region at the film/electrolyte interface and in the inner chromium oxide region at the film/metal interface. However, donor and acceptor densities are closely related to the surface roughness via the grit size of the wet SiC paper. An increase in capacitance leading to higher doping densities is manifested by an increase in grit size. These parameters are also frequency dependent. An investigation of the frequency dispersion in relation to the evolution of the surface roughness was performed by analysing the Bode plots through the impedance measurements. The photocurrent results, obtained for the oxide films formed on the different abraded AISI 304, show an increasing photoresponse with decreasing grit size. In spite of this, a constant value of the band gap energy was obtained whatever the oxide film considered. The photocurrent response near the absorption edge is also discussed. The photocurrent response at fixed wavelength and as a function of the applied potential is also influenced by the grit size. [ABSTRACT FROM AUTHOR]

Nickel-based superalloy is the most widely used and has the most stable high-temperature oxidation resistance, but its machinability is poor. Therefore, choosing the appropriate tool coating can improve the cutting efficiency and tool life. Based on the first principles, this paper explores the influence of adding the fourth element on the mechanical properties of Ti3AlN coating, establishes the unit cell models of Ti3AlN and Ti1.5AlX1.5N (X = Cr, Zr, V, Nb, Si) by using Materials Studio, and analyzes the change of elastic properties and electronic structure. The results show that the addition of Cr, V and Nb improves the resistance to external force, hardness, stiffness and toughness compared with that before doping. The hardness, stiffness and toughness of the doped Cr element increase the most. Their electronic structures are further analyzed to study the effect of doping elements on tool hardness. Comparing the d-band center change of doping atoms and Ti atoms, it is found that the doping elements affect the d-orbital distribution of Ti atoms and then change the hybrid peak. Based on this theory, the reason for hardness change is explained from the perspective of electronic structure. When the tool hardness increased, the service life of coated tool and machining efficiency in cutting nickel-based superalloy can be improved. It provides theoretical basis for the selection of tool coating for cutting difficult-to-machine materials such as nickel-based superalloy. [ABSTRACT FROM AUTHOR]

The realm of chemiresistive gas sensors has witnessed a notable surge in interest in two-dimensional (2D) materials. The advancement of high-performance 2D gas sensing materials necessitates a quantitative theoretical method capable of accurately predicting their response. In this context, we present our first-principles framework for calculating the response of 2D materials, incorporating both carrier concentration and mobility. We showcase our method by applying it to prototype NH3 sensing on 2D MoS2 and comparing the results with prior experiments in the literature. Our approach offers a thorough solution for carrier concentration, taking into account the electronic structure around the Fermi level. In conjunction with the mobility calculation, this enables us to provide a quantitative prediction of the response profile and limit of detection (LOD), yielding a notably improved alignment with prior experimental findings. Further analysis quantifies the contributions of carrier concentration and mobility to the overall response of 2D MoS2 to NH3. We identify that discrepancies in the charge-transfer-based method primarily stem from overestimating carrier concentrations. Our method opens exciting opportunities to explore carrier mobility-dominated sensing materials, facilitates efficient screening of promising gas sensing materials, and quantitative understanding of the sensing mechanism. [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]

Phases with spontaneous time-reversal (T ) symmetry breaking are sought after for their anomalous physical properties, low-dissipation electronic and spin responses, and information-technology applications. Recently predicted altermagnetic phase features an unconventional and attractive combination of a strong T -symmetry breaking in the electronic structure and a zero or only weak-relativistic magnetization. In this work, we experimentally observe the anomalous Hall effect, a prominent representative of the T -symmetry breaking responses, in the absence of an external magnetic field in epitaxial thin-film Mn5Si3 with a vanishingly small net magnetic moment. By symmetry analysis and first-principles calculations we demonstrate that the unconventional d-wave altermagnetic phase is consistent with the experimental structural and magnetic characterization of the Mn5Si3 epilayers, and that the theoretical anomalous Hall conductivity generated by the phase is sizable, in agreement with experiment. An analogy with unconventional d-wave superconductivity suggests that our identification of a candidate of unconventional d-wave altermagnetism points towards a new chapter of research and applications of magnetic phases. The classification of magnets now includes altermagnets which possess opposite-spin sublattices connected by rotation and share some features with ferro- and antiferromagnets. Here the authors report the anomalous Hall effect in Mn5Si3 and interpret the results in terms of a d-wave altermagnetic phase. [ABSTRACT FROM AUTHOR]

Molecular representation is critical in chemical machine learning. It governs the complexity of model development and the fulfillment of training data to avoid either over- or under-fitting. As electronic structures and associated attributes are the root cause for molecular interactions and their manifested properties, we have sought to examine the local electron information on a molecular manifold to understand and predict molecular interactions. Our efforts led to the development of a lower-dimensional representation of a molecular manifold, Manifold Embedding of Molecular Surface (MEMS), to embody surface electronic quantities. By treating a molecular surface as a manifold and computing its embeddings, the embedded electronic attributes retain the chemical intuition of molecular interactions. MEMS can be further featurized as input for chemical learning. Our solubility prediction with MEMS demonstrated the feasibility of both shallow and deep learning by neural networks, suggesting that MEMS is expressive and robust against dimensionality reduction. In machine learning of molecular properties, adequate molecular representation is crucial, as minor structural changes result in significant differences in the activity of interest. Here, the authors use a lower-dimensional representation of a molecular manifold to embed electronic attributes and retain the chemical intuition of molecular interactions, invariant to translational and rational degrees of freedom of the molecular surface, to ease model complexities and facilitate generalization even with relatively small datasets. [ABSTRACT FROM AUTHOR]

Quantum computers have a potential for solving quantum chemistry problems with higher accuracy than classical computers. Quantum computing quantum Monte Carlo (QC-QMC) is a QMC with a trial state prepared in quantum circuit, which is employed to obtain the ground state with higher accuracy than QMC alone. We propose an algorithm combining QC-QMC with a hybrid tensor network to extend the applicability of QC-QMC beyond a single quantum device size. In a two-layer quantum-quantum tree tensor, our algorithm for the larger trial wave function can be executed than preparable wave function in a device. Our algorithm is evaluated on the Heisenberg chain model, graphite-based Hubbard model, hydrogen plane model, and MonoArylBiImidazole using full configuration interaction QMC. Our algorithm can achieve energy accuracy (specifically, variance) several orders of magnitude higher than QMC, and the hybrid tensor version of QMC gives the same energy accuracy as QC-QMC when the system is appropriately decomposed. Moreover, we develop a pseudo-Hadamard test technique that enables efficient overlap calculations between a trial wave function and an orthonormal basis state. In a real device experiment by using the technique, we obtained almost the same accuracy as the statevector simulator, indicating the noise robustness of our algorithm. These results suggests that the present approach will pave the way to electronic structure calculation for large systems with high accuracy on current quantum devices. [ABSTRACT FROM AUTHOR]