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Enhanced Charge Transport and Increased Active Sites on α-Fe <sub/>2</sub> O <sub/>3</sub> (110) Nanorod Surface Containing Oxygen Vacancies for Improved Solar Water Oxidation Performance
摘要： The e?ect of oxygen vacancies (VO) on α-Fe2O3 (110) facet on the performance of photoelectrochemical (PEC) water splitting is researched by both experiments and density functional theory (DFT) calculations. The experimental results manifest that the enhancement in photocurrent density by the presence of VO is related with increased charge separation and charge-transfer e?ciencies. The electrochemical analysis reveals that the sample with VO demonstrates an enhanced carrier density and reduced charge-transfer resistance. The results of DFT calculation indicate that the better charge separation is also contributed by the decrease of potential on the VO surface, which improves the hole transport from the bulk to the surface. The reduced charge-transfer resistance is owing to the greatly increased number of active sites. The current study provides important insight into the roles of VO on α-Fe2O3 photoanode, especially on its surface catalysis. The generated lesson is also helpful for the improvement of other PEC photoanode materials.
关键词： oxygen vacancies,α-Fe2O3,photoelectrochemical water splitting,charge-transfer efficiencies,density functional theory,charge separation
更新于2025-09-23 15:21:21
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Stacking effect on electronic, photocatalytic and optical properties: A comparison between bilayer and monolayer SnS
摘要： In this work, the stacking-dependent optoelectronic performances of a bilayer SnS were explored based on density functional theory (DFT). The results demonstrated that an AB-stacking induces an indirect-to-direct transition, a feature that is capable of vanquishing electron transition impediment from an intrinsic indirect monolayer SnS. An anisotropic and small carrier effective mass exists in all the stacking models, among which the AB-stacking with the lowest value favors high carrier mobility. Calculated band alignments are indicative of acceptable and adjustable photocatalytic activity for all the stacking models, unlike the monolayer SnS. The AB-stacking configuration possesses the strongest redox power, which facilitates it to be a potential candidate for photocatalytic water splitting. Additionally, the AB-stacking does effectively improve optoelectronic properties. The study demonstrated that layer-stacking is an availably adjustable method in the fields of sunlight-driven photocatalysis for nano-optoelectronic devices.
关键词： Electronic properties,Density functional theory,Stacking models,Optical properties,Photocatalytic properties
更新于2025-09-23 15:21:21
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AIP Conference Proceedings [Author(s) DAE SOLID STATE PHYSICS SYMPOSIUM 2017 - Mumbai, India (26–30 December 2017)] - First principles calculations for interaction of tyrosine with (ZnO)3 cluster
摘要： First Principles Calculations have been performed to study interactions of Phenol ring of Tyrosine (C6H5OH) with (ZnO)3 atomic cluster. All the calculations have been performed under the Density Functional Theory (DFT) framework. Structural and electronic properties of (ZnO)3/C6H5OH have been studied. Gaussian basis set approach has been adopted for the calculations. A ring type most stable (ZnO)3 atomic cluster has been modeled, analyzed and used for the calculations. The compatibility of the results with previous studies has been presented here.
关键词： (ZnO)3 cluster,Tyrosine,First Principles Calculations,Density Functional Theory,Gaussian basis set
更新于2025-09-23 15:21:21
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Impact of Organic Spacers on the Carrier Dynamics in 2D Hybrid Lead-Halide Perovskites
摘要： We have carried out non-adiabatic molecular dynamics simulations combined with time-dependent density functional theory calculations to compare the properties of the two-dimensional (2D) (BA)2(MA)Pb2I7 and three-dimensional (3D) MAPbI3 (where MA = methylammonium and BA = butylammonium) materials. We evaluate the different impacts that the 2D-confined spacer layer of butylammonium cations and the 3D-confined methylammonium cations have on the charge carrier dynamics in the two systems. Our results indicate that while both the MA+ and BA+ cations play important roles in determining the carrier dynamics, the BA+ cations exhibit stronger non-adiabatic couplings with the 2D perovskite framework. The consequence is a faster hot-carrier decay rate in 2D (BA)2(MA)Pb2I7 than in 3D MAPbI3. Thus, tuning of the functional groups of the organic spacer cations in order to reduce the vibronic couplings between the cations and the Pb-I framework can offer the opportunity to slow down the hot-carrier relaxations and increase the carrier lifetimes in 2D lead-halide perovskites.
关键词： carrier dynamics,2D hybrid lead-halide perovskites,time-dependent density functional theory,non-adiabatic molecular dynamics,organic spacers
更新于2025-09-23 15:21:21
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: A first-principles study
摘要： For environmental reasons there is a need for alternative Cd-free buffer materials in Cu(In,Ga)(S,Se)2 (CIGSSe) based thin film solar cells. In this context, β-In2S3 is one candidate material, whose optoelectronic properties can be affected by the presence of impurities. In this study, we investigate the impact of O and Cl impurities on the electronic and optical behavior of β-In2S3 by means of electronic structure calculations within density functional theory using hybrid functionals. We find that β-In2S3 is thermodynamically stable being in contact with both O and Cl reservoirs. Furthermore, we present evidence that O on interstitial sites (Oi) and Cl on 8c In sites (ClIn) cause low-temperature persistent electron photoconductivity. At room temperature, defect levels associated with Cl on S sites (ClS, ClS(cid:2) , and ClS(cid:2)(cid:2) ) get thermally ionized and release free electrons into the system. Thus, the n-type conductivity of the In2S3 buffer layer increases. O impurities on S sites, in contrast, are electrically inert. Hence, we conclude that intentional doping by Cl is a means to improve the properties of β-In2S3 serving as buffer material.
关键词： β-In2S3,hybrid functionals,O and Cl impurities,n-type conductivity,density functional theory,persistent electron photoconductivity,electronic structure calculations
更新于2025-09-23 15:21:21
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Adsorption of the liquid crystal molecule 5CB on graphene
摘要： We use density functional theory to explore the stable adsorption geometries of the liquid crystal molecule 5CB on a graphene sheet. First, we calculate the dependence of the polarizability of 5CB on its geometry. Our results break down the contributions of the cyano, biphenyl, and alkyl groups to the optical properties of 5CB, confirming the biphenyl group as the most influential. Second, we quantify possible adsorption structures of 5CB on graphene. We find that 5CB can stably adsorb with its biphenyl group oriented intermediate to the armchair and zigzag crystallographic directions, in addition to adsorbing with the biphenyl oriented along those directions.
关键词： 5CB,graphene,density functional theory,liquid crystal,adsorption
更新于2025-09-23 15:21:21
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Density Functional Theory Calculations of Oxygen-Vacancy Formation and Subsequent Molecular Adsorption on Oxide Surfaces
摘要： The surface oxygen vacancy formation energy (EOvac) is an important parameter in determining the catalytic activity of metal oxides. Estimating these energies can therefore lead to data-driven design of promising catalyst candidates. In the present study, we determine EOvac for various insulating and semiconducting oxides. Statistical investigations indicate that the band gap, bulk formation energy, and electron affinity are factors that strongly influence EOvac. Electrons enter defect states after O desorption, and these states can be in the valence band, mid-gap, or in the conduction band. Subsequent adsorption of O2, NO, CO, CO2, and H2 molecules on an O-deficient surface is also investigated. These molecules become preferentially adsorbed at the defect sites, and EOvac is identified as the dominant factor that determines the adsorption mode as well as a descriptor that shows good correlation with the adsorption energy.
关键词： catalytic activity,molecular adsorption,oxygen vacancy formation energy,metal oxides,density functional theory
更新于2025-09-23 15:21:21
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The electronic and elasticity properties of new half-metallic chalcogenides Cu <sub/>3</sub> TMCh <sub/>4</sub> (TM?=?Cr, Fe and Ch?=?S, Se, Te): an <i>ab initio</i> study
摘要： The ternary copper-based chalcogenides Cu3TMCh4 (TM = Cr, Fe and Ch = S, Se, Te), which have simple cubic (SC) crystal structure and conform to P(cid:1)43m space group with 215 space number, have been investigated by spin-polarised generalised gradient approximation (GGA) in the framework of density functional theory (DFT). All systems have been considered in ferromagnetic (FM) order. The mechanical and thermal properties and the electronic band structures of these systems have been investigated after the well-optimised structural parameters have been obtained. The spin-polarised electronic band structures of all the systems exhibit half-metallic behaviour with band gaps in minority spin channel from 0.29 eV for Cu3FeTe4 to 1.08 eV for Cu3CrS4, while metallic band structures are observed for majority spins. This agrees with the calculated total magnetic moments which are close to integer values. The calculated negative formation enthalpies indicate the energetic and thermodynamic stability of these compounds. Moreover, the calculated elastic constants verify that these materials are stable mechanically due to satisfying Born stability criteria. The estimated anisotropy shear factors show that Cu3FeS4, Cu3FeSe4 and Cu3CrSe4 systems have nearly isotropic character with 1.004, 0.910, and 0.958 values, respectively, whereas other compounds have relatively low anisotropic behaviour.
关键词： electronic structure of bulk materials,density functional theory,chalcogenides,Half-metallic,mechanical properties of solids
更新于2025-09-23 15:21:21
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[IEEE 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Kyoto, Japan (2018.7.9-2018.7.13)] 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Field emission patterns from carbon nanotubes calculated by time-dependent density functional theory
摘要： We calculated the field emission patterns of various types of carbon nanotubes (CNTs). Regarding the near field regime, emission patterns of CNTs and hydrogen terminated CNTs (H-CNTs) well corresponds to the atoms located in the tube tip. We also found different focusing features; a focused-type and an unfocused-type. The beams from armchair (5,5) and (6,6) types are focused, while the beam from zigzag (9,0) types are unfocused.
关键词： field emission,carbon nanotubes,emission pattern,time dependent density functional theory,first principle calculation,ab initio calculation
更新于2025-09-23 15:21:21
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DFT study of the influence of acetyl groups of cellulose acetate on its intrinsic birefringence and wavelength dependence
摘要： The effect of the acetyl groups of cellulose acetate (CA) on its intrinsic birefringence and its wavelength dependence was investigated using density functional theory (DFT). Seven types of CA repeating-unit models that differ in their degree of substitution (DS) and substitution sites were used in the calculations. The results suggested that the intrinsic birefringence (Δn°) and its wavelength dependence significantly depended on the conformations of the acetyl group at C6. Additionally, the intrinsic birefringence of CA films was estimated as the ensemble average of the calculated Δn° values of the conformers. The increase in the DS of CA led to a more negative intrinsic birefringence and a larger wavelength dependence. The computational results were in good qualitative agreement with the experimental results and suggested that conformational variety and/or its control would be important factors for the design of optical films containing CA.
关键词： Cellulose acetate,Density functional theory,Computational chemistry,Birefringence
更新于2025-09-23 15:21:21