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Electronic, Optical and Elastic Properties of Cu2CdGeSe4: A First-Principles Study
摘要： Using the augmented plane wave + local orbitals method with different approximation functionals, we investigate systematically the electronic, optical and elastic properties of stannite-type Cu2CdGeSe4. Among different approximation functionals, the modi?ed Becke–Johnson (mBJ) potential with Hubbard-corrected parameter U (mBJ + U) gives the most reliable results on the electronic properties of Cu2CdGeSe4 in comparison with the experimental data. Elastic modulus, elastic constants and the Poisson’s ratio of Cu2CdGeSe4 were calculated using the Elastic software package. Optical properties such as wide spectrum of absorbed photon energy, namely 1.3–27.2 eV, high absorption coef?cient (above 104 cm?1) and optical anisotropy suggest the application of Cu2CdGeSe4 in solar cells.
关键词： electronic structure,optical properties,Optical materials,elastic properties,ab initio calculations
更新于2025-09-23 15:21:21
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Vibrational fingerprint of localized excitons in a two-dimensional metal-organic crystal
摘要： Long-lived excitons formed upon visible light absorption play an essential role in photovoltaics, photocatalysis, and even in high-density information storage. Here, we describe a self-assembled two-dimensional metal-organic crystal, composed of graphene-supported macrocycles, each hosting a single FeN4 center, where a single carbon monoxide molecule can adsorb. In this heme-like biomimetic model system, excitons are generated by visible laser light upon a spin transition associated with the layer 2D crystallinity, and are simultaneously detected via the carbon monoxide ligand stretching mode at room temperature and near-ambient pressure. The proposed mechanism is supported by the results of infrared and time-resolved pump-probe spectroscopies, and by ab initio theoretical methods, opening a path towards the handling of exciton dynamics on 2D biomimetic crystals.
关键词： FeN4 center,spin transition,ab initio theoretical methods,excitons,carbon monoxide,infrared spectroscopy,graphene,time-resolved pump-probe spectroscopy,two-dimensional metal-organic crystal
更新于2025-09-23 15:21:21
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Strongly Coupled Coherent Phonons in Single-Layer MoS <sub/>2</sub>
摘要： We present a transient absorption setup combining broadband detection over the visible-UV range with high temporal resolution (～20fs) which is ideally suited to trigger and detect vibrational coherences in different classes of materials. We generate and detect coherent phonons (CPs) in single layer (1L) MoS2, as a representative semiconducting 1L-Transition Metal Dichalcogenide (TMD), where the confined dynamical interaction between excitons and phonons is unexplored. The coherent oscillatory motion of the out-of-plane A'1 phonons, triggered by the ultrashort laser pulses, dynamically modulates the excitonic resonances on a timescale of few tens fs. We observe an enhancement by almost two orders of magnitude of the CP amplitude when detected in resonance with the C exciton peak, combined with a resonant enhancement of CP generation efficiency. Ab Initio calculations of the change in 1L-MoS2 band structure induced by the A'1 phonon displacement confirm a strong coupling with the C exciton. The resonant behavior of the CP amplitude follows the same spectral profile of the calculated Raman susceptibility tensor. These results explain the CP generation process in 1L-TMDs and demonstrates that CP excitation in 1L-MoS2 can be described as a Raman-like scattering process.
关键词： exciton-phonon interaction,Coherent phonons,transient absorption spectroscopy,transition metal dichalcogenides,ab-initio calculation
更新于2025-09-23 15:21:01
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High-throughput ab initio calculations on dielectric constant and band gap of non-oxide dielectrics
摘要： High-k dielectrics, materials having a large band gap (Eg) and high dielectric constant (k) simultaneously, constitute critical components in microelectronic devices. Because of the inverse relationship between Eg and k, materials with large values in both properties are rare. Therefore, massive databases on Eg and k will be useful in identifying optimal high-k materials. While experimental and theoretical data on Eg and k of oxides are accumulating, corresponding information is scarce for non-oxide dielectrics with anions such as C, N, F, P, S, and Cl. To identify promising high-k dielectrics among these material groups, we screen 869 compounds of binary carbides, nitrides, sulfides, phosphides, chlorides, and fluorides, through automated ab initio calculations. Among these compounds, fluorides exhibit an Eg-k relation that is comparable to that of oxides. By further screening over ternary fluorides, we identify fluorides such as BiF3, LaF3, and BaBeF4 that could serve as useful high-k dielectrics.
关键词： band gap,dielectric constant,High-k dielectrics,non-oxide dielectrics,ab initio calculations
更新于2025-09-23 15:21:01
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On the Construction of Quasi-Diabatic Hamiltonians That Accurately Represent Ab Initio Determined Adiabatic Electronic States Coupled by Conical Intersections for Systems With on the Order of 15 Atoms. Application to Cyclopentoxide Photoelectron Detachment in the Full 39 Degrees of Freedom
摘要： We present, for systems of moderate dimension, a fitting framework to construct quasi-diabatic Hamiltonians that accurately represent ab initio adiabatic electronic structure data including the effects of conical intersections. The framework introduced here minimizes the difference between the fit prediction and the ab initio data obtained in the adiabatic representation, which is singular at a conical intersection seam. We define a general and flexible merit function to allow arbitrary representations and propose a representation to measure the fit-ab initio difference at geometries near electronic degeneracies. A fit Hamiltonian may behave poorly in insufficiently sampled regions, in which case a machine learning theory analysis of the fit representation suggests a regularization to address the deficiency. Our fitting framework including the regularization is used to construct the full 39-dimensional coupled diabatic potential energy surfaces for cyclopentoxy relevant to cyclopentoxide photoelectron detachment.
关键词： cyclopentoxide photoelectron detachment,quasi-diabatic Hamiltonians,ab initio electronic structure,potential energy surfaces,conical intersections
更新于2025-09-23 15:21:01
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Chromophores in cellulosics, XVIII. Degradation of the cellulosic key chromophore 5,8-dihydroxy-[1,4]-naphthoquinone under conditions of chlorine dioxide pulp bleaching: a combined experimental and theoretical study
摘要： DHNQ is one of the key chromophores occurring in all types of aged cellulosics. This study investigates the degradation of DHNQ by chlorine dioxide at moderately acidic (pH 3) conditions, corresponding to the conditions of industrial bleaching ("D stage"). The degradation involves three major pathways. As initial reaction, a hydrogen transfer from DHNQ to chlorine dioxide via a PCET mechanism occurs to form a radical DHNQ(cid:2) and chlorous acid. DHNQ(cid:2) is then attacked by water to give a pentahydroxynaphthalene radical PHN(cid:2) that is stabilized by strong delocalization of the non-paired electron into its aromatic ring. PHN(cid:2) immediately disproportionates to give the observable intermediate 1,2,4,5,8-pentahydroxynapththalene (I), which was comprehensively con?rmed by NMR and MS (path A). In the presence of excess ClO2, I is immediately further oxidized into acetic acid, glycolic acid, oxalic acid and CO2 as the ?nal, stable, and non-colored products (path C). In the absence of excess ClO2, elimination of water from I regenerates DHNQ (path B), so that at roughly equimolar DHNQ/ClO2 ratios ClO2 is fully consumed while a major part of DHNQ is recovered. To avoid such DHNQ "recycling" under ClO2 consumption—and to completely degrade DHNQ to colorless degradation products instead—ClO2 must be applied in at least ?vefold molar excess relative to DHNQ.
关键词： Density functional theory (DFT),Ab initio calculations,Yellowing,Cellulose,Brightness,Chromophores,5,8-dihydroxy-[1,4]-naphthoquinone,Chlorine dioxide,Brightness reversion,Pulp bleaching
更新于2025-09-23 15:21:01
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<i>Ab initio</i> study of parity and time-reversal violation in laser-coolable triatomic molecules
摘要： Electronic structure enhancement factors of simultaneous parity and time-reversal violation (P, T violation) caused by an electric dipole moment of the electron (eEDM) and scalar-pseudoscalar nucleon-electron current (SPNEC) interactions are reported for various metal monohydroxides, several of which are considered laser-coolable and promising candidates for an eEDM measurement. Electronic structure enhancements are calculated ab initio within zeroth-order regular approximation (ZORA) for CaOH, SrOH, BaOH, RaOH, and YbOH. Scaling behavior with respect to nuclear charge numbers and the ratio of enhancement factors for both discussed sources of P, T violation are analyzed, which are crucial to obtaining stringent bounds on parameters for new physics from experiments.
关键词： laser-coolable molecules,electric dipole moment,ab initio calculation,scalar-pseudoscalar nucleon-electron current,parity and time-reversal violation,ZORA
更新于2025-09-23 15:21:01
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Effect of DFT methods on electronic structure and <i>K</i> -absorption spectra of InPS <sub/>4</sub> : detailed studies of the optical, thermoelectric and elastic properties
摘要： The effect of exchange-correlation potential on InPS4 electronic structure was studied by applying GGA, GGA+U, mBJ, and mBJ+U potentials in the Kohn–Sham framework. The use of mBJ+U in full potential APW+lo method results in reliable K-absorption spectrum, which consists of nearly full experimental peaks of right intensity. The remarkable discrepancy between 1e w^( ) and 1e w?( ) occurs at 0 eV, 4 eV, 6 eV, and 9.5 eV, indicating the strong anisotropic optical properties of InPS4 at these energy levels. At 4 eV, the optical absorption of InPS4 has high order of 105cm?1 magnitude for wide energy range, at least within 4–20 eV. The figure of merit ZT achieves its highest value of about 0.8–1. InPS4 is a p-type semiconductor for chemical potential μ ranging from 0 eV to about 1.6 eV, but it is an n-type semiconductor for μ of about 1.6–2.7 eV. The Poisson’s ratio is equal to 0.26 and B/G@1.75. Indium thiophosphate InPS4 possesses rather low deformation resistance with the Young and shear moduli of 38.47 GPa and 15.27 GPa, respectively.
关键词： thermoelectric properties,elastic properties,optical properties,ab initio calculations,x-ray spectrum
更新于2025-09-23 15:19:57
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[Springer Series on Atomic, Optical, and Plasma Physics] Gaseous Ion Mobility, Diffusion, and Reaction Volume 105 || Summary and Prognosis
摘要： Gaseous ion mobility, diffusion, and reaction have been studied by swarm techniques for about 120 years. Many important discoveries have been made, including the existence of electrons, ions, and isotopes; verification of quantum mechanics; the NTE equation; the tensorial nature of diffusion coefficients; and the usefulness of DTMS for studying ion–neutral reactions. The chapter reviews the progress in theoretical descriptions, numerical methods, and ab initio calculations of transport coefficients, highlighting the need for further research in molecular ion–neutral systems and the potential of models in understanding gaseous ion data.
关键词： DTMS,ion–neutral reactions,Boltzmann equation,swarm techniques,gaseous ion mobility,ab initio calculations,diffusion,IMS
更新于2025-09-23 15:19:57
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Structural and thermodynamic properties of cubic sphalerite aluminum nitride under hydrostatic compression
摘要： The present work aims to investigate the structural phase stability and thermodynamic properties of aluminium nitride with cubic zinc-blende structure at normal and high pressures (up to 5 GPa) and high temperatures (up to 2000 K). In this study, we use the pseudopotential plane wave method within the framework of the density functional theory with the local density approximation for the exchange-correlation functional. The phase transition pressure has been determined and found to be in very good agreement with several theoretical data. The pressure and temperature dependences of thermodynamic properties are successfully presented, analyzed and discussed in details. Besides, the plasmon energy and microhardness are examined.
关键词： High-pressure,Ab-initio calculation,High-temperature,Thermodynamic properties,Aluminium nitride
更新于2025-09-23 15:19:57