The structural, electronic, dipole-induced internal electric field, optical and photocatalytic properties of monolayer GeS and GeSe under external biaxial strain were investigated by using ...first-principles calculations. The monolayer GeS and GeSe are indirect semiconductors with the band gaps of 3.265 eV and 2.993 eV, respectively. The band alignment of the monolayer GeS and GeSe manifests the photocatalytic activity for water splitting. Especially, it is effective to tune the properties including structures, band gaps, surface potential difference, dipole moment P, dipole-induced internal electric field, absorption and photocatalytic activity of the monolayer GeS and GeSe via biaxial strain. Our results suggest that monolayer GeS and GeSe possess photocatalytic properties for water splitting, and strain engineering, especially tensile strain, can enhance the photocatalytic activity under ultraviolet and visible light.
Low-dimensional, lead-free, and cuprous-based halide compounds of Cs3Cu2Br5 micro-rods and CsCuBr2 micro-crosses (MCs) were synthesized via a simple solution method. The CsCuBr2 MCs were quite stable ...in air. Distinct green electroluminescence at 527 nm originating from CsCuBr2 MCs was observed at a low driving voltage of less than 3 V.
The first-principles method of density functional theory (DFT) is used to study the structural stability and electrochemical properties of B doped graphene with concentrations of 3.125%, 6.25% and ...18.75% respectively, and their lithium storage mechanism and characteristics are further studied. The results show that the doped systems all have negative adsorption energy, indicating that the structures can exist stably, and the adsorption energy of lithium ions on graphene decreases with the increase of B doping concentration. Among them, the B
6
C
26
structure has the lowest adsorption energy and can adsorb more lithium ions. The density of states indicates that doping with B can increase the conductivity of graphene greatly. Subsequently, the CI-NEB method to search for the transition state of the doped structure is used, showing that the B
6
C
26
structure has the lowest diffusion barrier and good rate performance. Therefore, these findings provide a certain research foundation for the development and application of lithium-ion battery anode materials.
Using the DFT method, B-doped graphene with different concentrations shows excellent structural stability, electrochemical performance and strong lithium storage ability, which provides a research strategy for the application of anode materials.
The structural stability and electrochemical performance of intrinsic and B doped T-graphene nanotubes with different tube lengths are systematically studied by using first-principles calculations ...within the framework of density functional theory (DFT). The results show that with the increase of tube length, the adsorption energy of both intrinsic and B doped T-graphene nanotubes exhibits regular oscillations, and B doping is beneficial for elevating the adsorption ability of T-graphene nanotubes. The density of states show that intrinsic T-graphene nanotubes are zero band gap semiconductors, and the orbitals' electronic states cross the Fermi level to form a p-type semiconductor, indicating that B doping greatly improves the conductivity of the system. The results of migration behavior demonstrate that B doping can effectively reduce the diffusion barrier of lithium ions on their surface, especially in B doped T-graphene nanotubes with a tube length of
N
= 1, resulting in more effective migration behavior and excellent rate performance. These findings provide a theoretical basis for the development and application of negative electrode materials for lithium-ion batteries.
DFT calculations show that the intrinsic and B doped T-graphene nanotubes exhibit different properties for different tube lengths.
Using first-principles calculation based on density functional theory, the effects of B, Al and B-Al doping on the structural stability and electrochemical properties of silicene were systematically ...studied, and their potential as anode materials for lithium ion batteries was evaluated. The calculated results of formation energy indicate that the doped system has good stability. The charge density difference and density of states show that doping can improve the conductivity of silicene, and enhance the interaction with Li. Moreover, on the surface of B, Al and B-Al doped silicene, the diffusion barriers of the most easily migrated path for Li ions are 0.22 eV, 0.19 eV, and 0.21 eV, respectively, suggesting that all doped systems have good Li ion migration rates. And the open circuit voltage is between 0.40 V and 0.54 V, which is relatively stable and low. Therefore, B, Al and B-Al doping can effectively regulate the structural stability and electrochemical performance of silicene, which provides a theoretical basis for the experimental preparation of excellent silicene anode materials.
B, Al and B-Al doped silicene show excellent structural stability, electrochemical performance and strong lithium storage ability.
Despite outstanding and unique properties, the structure-property relationship of high entropy alloys (HEAs) is not well established. The machine learning (ML) is used to scrutinize the effect of ...nine physical quantities on four phases. The nine parameters include formation enthalpies determined by the extended Miedema theory, and mixing entropy. They are highly related to the phase formation, common ML methods cannot distinguish accurately. In this paper, feature selection and feature variable transformation based on Kernel Principal Component Analysis (KPCA) are proposed, the feature variables are optimized, the distinction of phases is carried out by Support vector machine (SVM) model. The results indicate that elastic energy and atom-size difference contribute significantly in the formation of different phases. The accuracy of testing set predicted by SVM based on four feature variables and KPCA (4V-KPCA) is 0.9743. The F1-scores predicted detailedly by SVM based on 4V-KPCA for the considered alloy phases are 0.9787, 0.9463, 0.9863 and 0.8103, corresponding to solid solution, amorphous, the mixture of solid solution and intermetallic, and intermetallic respectively. The extended Miedema theory provides accurate thermodynamic properties for the design of HEAs, and ML methods (especially SVM combined KPCA) are powerful in the prediction of alloy phases.
Display omitted
•The accurate thermodynamic properties of alloys can be calculated quickly by extended Miedema theory•The feature variables are optimized by Kernel Principal Component Analysis.•The phases of multi-principal element alloys are distinguished well by support vector machine of machine learning model.
The construction of van der Waals heterostructures based on 2D polarized materials is a unique technique to achieve enhanced photocatalytic performance. We have investigated the intrinsic electric ...field and photocatalytic properties of the MoTe2/GeS heterostructure via first-principles calculations. The results showed that a dipole-induced electric field induced by the GeS monolayer and an interface-induced electric field induced by the interface between the GeS monolayer and the MoTe2 monolayer emerge in the 2D polarized MoTe2/GeS heterostructure. The dipole-induced electric field contributes mainly to the total intrinsic electric field. Moreover, the 2D polarized MoTe2/GeS heterostructure possesses many excellent and distinguished photocatalytic performance parameters, such as a direct semiconductor bandgap of 1.524 eV, a wide light spectrum ranging from the ultraviolet to near-infrared region with a high absorption coefficient (about 106 cm−1), a total intrinsic electric field, which reduces the probability of the recombination of photo-generated electron–hole pairs effectively, and a suitable band alignment for the water-splitting reaction. These indicate that the 2D polarized MoTe2/GeS van der Waals heterostructure is a potential novel high-efficient photocatalyst for water-splitting.
Wide-bandgap lead-free copper(i) halides have attracted considerable attention in fabricating optoelectronic devices, especially for high-performance ultraviolet (UV) photodetectors (PDs). However, ...the metal–semiconductor–metal structures that are frequently used in the UV PDs hinder further performance improvement due to the poor separation of photo-generated carriers. In this work, we demonstrated a heterostructured self-powered UV PD using lead-free copper(i) halide Cs3Cu2I5 microcrystals (MCs) that had a curious X chromosome-shaped morphology on p-Si substrates. The X chromosome-shaped Cs3Cu2I5 MCs showed distinct blue emission at 441 nm and exhibited high stability under ambient air conditions. By introducing a thin polymethyl methacrylate (PMMA) film as modification for the interface, the heterostructured UV PD showed a remarkable responsivity of 15.2 mA W−1 for an ultralow light intensity of 0.422 μW cm−2, a specific detectivity of 8.1 × 1011 Jones, an on/off ratio of up to 4.14 × 103, and a response time of 41.43 ms/47.84 ms under 298 nm UV irradiation at zero bias. Notably, the on/off ratio was nearly 450 times higher than that of the device without X chromosome-shaped Cs3Cu2I5 MCs. The unencapsulated device exhibited extraordinary stability with no significant reduction in the photocurrent even after continuous operation for 8 hours or storage in ambient air for 60 days. Our work introduces a feasible approach that uses lead-free copper(i) halide Cs3Cu2I5 in future high-performance self-powered UV photodetection applications.
Herein, the feasibility of Fe substitution by Ga, Ge and As in Li2FeSiO4 in modulating its structural, mechanical, electrochemical, capacity and electronic properties was systematically studied via ...first-principles calculations based on density functional theory within the generalized gradient approximation with Hubbard corrections (GGA+U). The calculated results show that Ga, Ge and As doping can effectively reduce the range of the cell volume change during Li+ removal, improving the Li+ detachment ability and cycle stability of the system. Meanwhile, the calculated mechanical properties including modulus ratio, B/G, and Poisson ratio, ν, indicate that the doped systems of Ga, Ge and As exhibit excellent mechanical properties. In addition, besides the increase in theoretical average deintercalation voltage induced by the Ga dopant when more than one Li+ ion is removed in the formula unit, the doping of Ga, Ge and As all reduce the theoretical average deintercalation voltage in the process of Li+ extraction. Especially in the case of doping of Ge, when 0.5 Li+ is removed from LiFe0.5Ge0.5SiO4, the theoretical average deintercalation voltage only increases by 0.19 V compared with the case of the removal of one Li+ in Li2Fe0.5Ge0.5SiO4, which causes the cathode material to have a longer and more stable discharge platform. Moreover, in the process of Li+ removal, the doping of Ga, Ge and As can effectively participate in the charge compensation of the system, and Ge and As can provide further charge, increasing the capacity of the Li2FeSiO4 cathode material considerably.
The friction between a molybdenum disulphide (MoS
2
) nanoflake and a MoS
2
substrate was analyzed using a modified Tomlinson model based on atomistic force fields. The calculations performed in the ...study suggest that large deformations in the substrate can induce a dramatic decrease in the friction between the nanoflake and the substrate to produce the so-called superlubricity. The coefficient of friction decreases by 1–4 orders of magnitude when a high strain exceeding 0.1 is applied. This friction reduction is strongly anisotropic. For example, the reduction is most pronounced in the compressive regime when the nanoflake slides along the zigzag crystalline direction of the substrate. In other sliding directions, the coefficient of friction will reduce to its lowest value either when a high tensile strain is applied along the zigzag direction or when a high compressive strain is applied along the armchair direction. This anisotropy is correlated with the atomic configurations of MoS
2
.
PDF
