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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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Majorization preservation of Gaussian bosonic channels
摘要： It is shown that phase-insensitive Gaussian bosonic channels are majorization-preserving over the set of passive states of the harmonic oscillator. This means that comparable passive states under majorization are transformed into equally comparable passive states by any phase-insensitive Gaussian bosonic channel. Our proof relies on a new preorder relation called Fock-majorization, which coincides with regular majorization for passive states but also induces another order relation in terms of mean boson number, thereby connecting the concepts of energy and disorder of a quantum state. The consequences of majorization preservation are discussed in the context of the broadcast communication capacity of Gaussian bosonic channels. Because most of our results are independent of the speci?c nature of the system under investigation, they could be generalized to other quantum systems and Hamiltonians, providing a new tool that may prove useful in quantum information theory and especially quantum thermodynamics.
关键词： quantum channels,majorization theory,passive states,gaussian bosonic channels,quantum optics
更新于2025-09-23 15:21:21
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In-situ measurement of surface relief induced by Widmanst?tten and bainitic ferrites in low carbon steel by digital holographic microscopy
摘要： In-situ measurement by digital holographic microscopy (DHM) was employed to clarify the difference between the surface relief effects of Widmanst?tten ferrite (WF) and bainitic ferrite (BF) associated with their transformations from austenite in a low-carbon steel. It was clarified that the evolution of the surface relief is totally different between WF and BF. Only in BF, the observed ratio of the relief height to the plate width converged instantly to the value predicted by the phenomenological theory of martensite crystallography (PTMC). The ratio gradually increased with increasing plate thickness and never reached the value predicted by PTMC in WF.
关键词： Digital holographic microscopy,Phase transformations,Surface relief,Phenomenological theory of martensite crystallography
更新于2025-09-23 15:21:21
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MCMC determination of the cosmic UV background at <i>z</i> ? 0 from Hα fluorescence.
摘要： In a recent paper (Fumagalli et al. 2017) we reported on the detection of a di?use Hα glow in the outskirts of the nearby, edge-on disc galaxy UGC 7321 observed with the Multi Unit Spectroscopic Explorer (MUSE) at the ESO Very Large Telescope. By interpreting the Hα emission as ?uorescence arising from hydrogen ionised by an external (i.e., extragalactic) radiation ?eld, we estimated the UV background (UVB) intensity in terms of H I ionisation rate (per ion) at z (cid:39) 0 to be in the range ΓHI ～ 6 ? 8 × 10?14 s?1. In the present work, by performing radiative transfer calculations over a large set of models of the gaseous disc of UGC 7321, we re?ne our estimate and through an MCMC analysis derive a value for the photoionisaton rate of ΓHI = 7.27+2.93 ?2.90 × 10?14 s?1. In particular, our analysis demonstrates that this value is robust against large variations in the galaxy model and that the uncertainties are mainly driven by the errors associated with the observed Hα surface brightness. Our measurement is consistent with several recent determinations of the same quantity by a completely independent technique (i.e., ?ux decrement analysis of the Lyα-forest), and support the notion that the low redshift UVB is largely dominated by active galactic nuclei (AGNs), possibly with no need of further contribution from star forming galaxies.
关键词： radiative transfer,methods: numerical,cosmology: theory,intergalactic medium
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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Salt Effect in Ion-Pair Dynamics after Bimolecular Photoinduced Electron Transfer in a Room-Temperature Ionic Liquid
摘要： Bimolecular photoinduced electron transfer between perylene and two quenchers was investigated in an imidazolium room-temperature ionic liquid (RTIL) and in a dipolar solvent mixture of the same viscosity using transient absorption on the subpicosecond to submicrosecond timescales. Whereas charge separation dynamics were similar in both solvents, significant differences were observed in the temporal evolution of the ensuing radical ions: although small, the free ion yield is significantly larger in the RTIL, and recombination of the ion pair to the triplet state of perylene is more efficient in the dipolar solvent. The temporal evolution of reactant, ion and triplet state populations could be well reproduced using Unified Encounter Theory. This analysis reveals that the observed differences can be explained by the strong screening of the Coulomb potential in the ion pair by the ionic solvent. In essence, RTILs favor free ions compared to highly dipolar solvents of the same viscosity.
关键词： unified encounter theory,free ions,spin conversion,charge recombination,transient absorption,charge separation
更新于2025-09-23 15:21:21