- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Optical properties of shortest-width zig-zag Silicene nano-ribbons: effects of local fields
摘要： We have computed from first principles the structural, magnetic and optical properties of zig-zag oriented silicene nanoribbons. The minimal width for structurally stable planar structure having zig-zag edges corresponds to a 4-chains ribbon. Its ground state presents reconstructed and spin polarized edges, coupled antiferromagnetically. For this state, and for the corresponding excited state with ferromagnetically coupled edges, we computed the optical absorption spectra within the independent particle approximation, including local field effect corrections, for light polarized in the directions parallel and perpendicular to the ribbon axis. For the “parallel” light polarization the inclusion of local fields effects is limited to a slight reduction of the intensity of the main peak in the infrared region, as well as that of some minor peaks in the visible-ultraviolet structure. Conversely, the computed optical spectrum for light polarized perpendicularly to the ribbon axis shows that the short-width zig-zag nanoribbons are basically transparent in the infrared and visible region, because of the effect of electronic confinement combined with local fields.
关键词： local fields,silicene nanoribbons,optical properties,zig-zag edges,first principles
更新于2025-09-23 15:21:01
-
Insights into Interfaces, Stability, Electronic Properties, and Catalytic Activities of Atomically Precise Metal Nanoclusters from First Principles
摘要： Atomically precise, ligand-protected metal nanoclusters are of great interest for their well-defined structures, intriguing physicochemical properties, and potential applications in catalysis, biology, and nanotechnology. Their structure precision provides many opportunities to correlate their geometries, stability, electronic properties, and catalytic activities by closely integrating theory and experiment. In this Account, we highlight recent theoretical advances from our efforts to understand the metal?ligand interfaces, the energy landscape, the electronic structure and optical absorption, and the catalytic applications of atomically precise metal nanoclusters. We mainly focus on gold nanoclusters. The bonding motifs and energetics at the gold?ligand interfaces are two main interests from a computational perspective. For the gold?thiolate interface, the ?RS?Au?SR? staple motif is not always preferred; in fact, the bridging motif (?SR?) is preferred at the more open facets such as Au(100) and Au(110). This finding helps understand the diversity of the gold?thiolate motifs for different core geometries and sizes. A great similarity is demonstrated between gold?thiolate and gold?alkynyl interfaces, regarding formation of the staple-type motifs with PhC≡C? as an example. In addition, N-heterocyclic carbenes (NHCs) without bulky groups also form the staple-type motif. Alkynyls and bulky NHCs have the strongest binding with the gold surface from comparing 27 ligands of six types, suggesting a potential to synthesize NHC-protected gold clusters. The energy landscape of nanosystems is usually complex, but experimental progress in synthesizing clusters of the same Au?S composition with different R groups and isomers of the same Aun(SR)m formula have made detailed theoretical analyses of energetic contributions possible. Ligand?ligand interactions turn out to play an important role in the cluster stability, while metastable isomers can be obtained via kinetic control. Although the superatom-complex theory is the starting point to understand the electronic structure of atomically precise gold clusters, other factors also greatly affect the orbital levels that manifest themselves in the experimental optical absorption spectra. For example, spin?orbit coupling needs to be included to reproduce the splitting of the HOMO?LUMO transition observed experimentally for Au25(SR)18?, the poster child of the family. In addition, doping can lead to structural changes and charge states that do not follow the superatomic electron count. Atomically precise metal nanoclusters are an ideal system for understanding nanocatalysis due to their well-defined structures. Active sites and catalytic mechanisms are explored for selective hydrogenation and hydrogen evolution on thiolate-protected gold nanoclusters with and without dopants. The behavior of H in nanogold is analyzed in detail, and the most promising site to attract H is found to be coordinately unsaturated Au atoms. Many insights have been gained from first-principles studies of atomically precise, ligand-protected gold nanoclusters. Interesting and important questions remaining to be addressed are pointed out in the end.
关键词： atomically precise metal nanoclusters,gold nanoclusters,catalytic activities,first principles,metal?ligand interfaces,electronic properties
更新于2025-09-23 15:21:01
-
Theoretical design of InSe/GaTe VDW heterobilayer: A potential visible-light photocatalyst for water splitting
摘要： Using first-principles calculations, we show that two-dimensional (2D) van der Waals (vdW) InSe/GaTe heterobilayer (HBL) can serve as a potential visible-light-driven photocatalyst for water splitting to produce hydrogen, which notably improves the photocatalytic performance over isolated InSe and GaTe monolayers. The type-II band alignment and high carrier mobility of the InSe/GaTe HBL facilitate the spatial separation of photo-generated carriers and thus enhances the photocatalytic efficiency. Meanwhile, the separated absorption of H+ and OH- on the surfaces of InSe/GaTe HBL is beneficial to the photocatalytic redox reactions. Moreover, InSe/GaTe HBL can significantly extend the range of light harvesting from visible-light to infrared-light. The predicted maximum power conversion efficiency (PCE) attains 12.3%. These results indicate the InSe/GaTe HBL is a promising photocatalyst for water splitting.
关键词： water splitting,InSe/GaTe heterobilayer,photocatalyst,first-principles calculations,visible-light
更新于2025-09-23 15:21:01
-
Unexpected robustness of the band gaps of TiO <sub/>2</sub> under high pressures
摘要： Titanium dioxide (TiO2) is a wide band gap semiconducting material which is promising for photocatalysis. Here we present first-principles calculations to study the pressure dependence of structural and electronic properties of two TiO2 phases: the cotunnite-type and the Fe2P-type structure. The band gaps are calculated using density functional theory with the generalized gradient approximation, as well as the many-body perturbation theory with the GW approximation. The band gaps of both phases are found to be unexpectedly robust across a broad range pressures. The corresponding pressure coefficients are significantly smaller than that of diamond and silicon carbide, whose pressure coefficient is the smallest value ever measured by experiment. The robustness originates from the synchronous change of valence band maximum and conduction band minimum with nearly identical rates of changes. A step-like jump of band gaps around the phase transition pressure point is expected and understood in light of the difference in crystal structures.
关键词： band gap,robustness,TiO2,first-principles calculations,high pressure
更新于2025-09-23 15:21:01
-
Surface Photocatalytic Research of Fe -doped TiO2 (001) Based On the First-principles
摘要： In this paper,the first-principles based on density functional theory was used to study the Fe/TiO2(001) band gap width and adsorption energy of C6H6 molecules at different positions on the surface of the molecule with different doping methods and different Fe content. Calculation of the band structure and density of states of Fe-doped TiO2 nanoparticles shows that, the surface gap doping is more favorable than the substitution doping to reduce the band gap of TiO2,and when the doping concentration is 6.122%,the maximum reduction of the band gap width is 59.3% higher than that of pure TiO2.According to the comparement of adsorption energy, it works out that the benzene molecule is mainly about horizontal adsorption on the surface of TiO2(001).Within the scope of the study, with the increase of Fe doping concentration, The adsorption energy does not decrease as the band gap, when the Fe atoms doping concentration is 4.167%,the maximum increase of adsorption energy is 63.2%.
关键词： photocatalytic,Fe-doped TiO2,band gap,first-principles,adsorption energy
更新于2025-09-23 15:21:01
-
Theoretical characterization of strain and interfacial electronic effects in donor-acceptor bilayers of 2D transition metal dichalcogenides
摘要： Amine Slassi1, Jér?me Cornil1,* E-mail : jerome.cornil@umons.ac.be Bilayers of 2D Transition Metal Dichalcogenides 1Laboratory for Chemistry of Novel Materials, University of Mons, BE-7000 Mons, Belgium Theoretical Characterization of Strain and Interfacial Electronic Effects in Donor-Acceptor Two-dimensional (2D) materials and their van der Waals (vdW) stacked hetero-structures are promising candidates for highly efficient (opto)-electronic applications. The performance of vdW these properties are affected when building a bilayer. We focus on MoS2-based bilayers, including MoS2/MoS2, WS2/MoS2, MoSe2/MoS2 and WSe2/MoS2 structures. The impact of properties of two-dimensional transition metal dichalcogenide (TMDs) monolayers and the way vacancies on the interlayer interactions is also investigated. The main finding of our calculations first?principle calculations, we have explored systematically the structural and electronic is that changes in the properties of 2D monolayers upon building stack do occur and are driven by heterostructures in devices strongly depend on electronic processes at their interfaces. Here, using both strain effects and interfacial electronic processes.
关键词： defect vacancy,first-principles calculations,vdW heterostructures,electronic processes,strain effects
更新于2025-09-23 15:21:01
-
First-Principles Study of Electronic Structure, Optical Properties and LO-TO Splitting of GaP
摘要： The electronic structure and optical properties of GaP were calculated using generalized gradients in density functional theory. The Bonn effective charge, optical frequency dielectric constant and the LO-TO splitting value were calculated by density functional theory perturbation method.
关键词： Splitting of LO-TO,Electrical and optical properties,GaP,First principles
更新于2025-09-23 15:21:01
-
Enhanced Photocatalytic Activity of 2 <i>H</i> -MoSe <sub/>2</sub> by 3 <i>d</i> Transition Metal Doping
摘要： To develop MoSe2-based photocatalysts, increasing the catalytic activity of 2H-MoSe2 is essential. In this work, the electronic and photocatalytic properties of 3d transition metal (TM) doped (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn) 2H-MoSe2 were investigated by first-principles calculations. The results indicate that Sc, Ti, V, Cr, Mn, Fe and Co atoms tend to substitute the Mo atoms under Se-rich condition, while Ni, Cu and Zn atoms prefer to occupy the interstitial positions. More importantly, Sc- and Ti-doped 2H-MoSe2 can enhance the photocatalytic activity by increasing the oxidizability of photogenerated holes, suppressing the recombination of photogenerated carriers and increasing the number of catalytic active sites.
关键词： photocatalytic activity,2H-MoSe2,3d transition metal doping,electronic properties,first-principles calculations
更新于2025-09-23 15:21:01
-
First-principle study of g-AlxGa1-xN alloys: planar and buckled structures
摘要： The fundamental properties of g-AlxGa1-xN alloys with planar and buckled structures are investigated based on the first-principles. The results show that the band gaps of g-AlxGa1-xN alloys can be tuned, making them promising candidate materials for future light-emitting applications. For two-dimensional planar single layer structures, the band gap of g-AlxGa1-xN alloy increase monotonically with the increase of Al concentration. In contrast, for the buckled structures, as Al concentration increases, the band gap of the alloy structure first increase and then decrease, for the Al0.5Ga0.5N alloy, maximum band gap values can be achieved. The ε peaks and absorption coefficients of planar structures blue-shift, but those of the buckled structures red-shift. The absorption coefficients of the two type structures show two distinct absorption peaks in the deep ultraviolet, therefore deep ultraviolet emission is considered to be a remarkable feature of g-AlxGa1-xN alloys, indicating the potential use of g-AlxGa1-xN alloys for future UV luminescence applications.
关键词： g-AlxGa1-xN alloys,Electronic structure,Optical properties,Two-dimensional material,The first principles
更新于2025-09-23 15:19:57
-
with Optimal Band Gap for Photovoltaics and Defect-Insensitive Blue Emission
摘要： Despite rapid progress in the power-conversion efficiency of Pb-based perovskite solar cells, both the long-term instability and Pb toxicity are still the main challenges for their commercial applications. Here, by first-principles GW calculations, we find three kinds of two-dimensional (2D) 111-type Pb-free In-based halide perovskites of the form Cs3In2X9 (X = Cl, Br, I) as promising alternatives to the star material CH3NH3PbI3 (MAPbI3) because of the following excellent electronic, optical, and transport properties: (i) The 2D In-based halide perovskites are environmentally friendly lead-free materials. (ii) Compared with MAPbX3, they have greater structural stability. (iii) As energetic photovoltaic materials, 2D Cs3In2I9 perovskites are direct-band-gap semiconductors with optimal band gaps from 1.25 eV (trilayer) to 1.47 eV (monolayer). (iv) The 2D Cs3In2X9 perovskites have ideal band structures for solid-state lighting with a wide direct-optical-band-gap range (approximately 0.94–3.54 eV), covering the whole visible-light region, and light electron (heavy hole) effective mass, which will directly enhance the defect-insensitive emission efficiency due to the localization of holes. Particularly, Cs3In2BrxCl9?x has a suitable direct optical band gap for highly desired blue emission. (v) The absorption coefficient of Cs3In2X9 is up to 7 × 104 cm?1, which is between that of GaAs (104 cm?1) and that of MAPbI3 (105 cm?1). (vi) The estimated power-conversion efficiency in Cs3In2I9 reaches 28%, which is close to that of MAPbI3 (30%). These findings pave a way for designing nontoxic, stable, and high-performance photovoltaic and light-emitting devices.
关键词： light-emitting devices,photovoltaics,halide perovskites,lead-free,two-dimensional,first-principles calculations
更新于2025-09-23 15:19:57