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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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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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<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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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
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Effect of Net Charge on the Relative Stability of 2D Boron Allotropes
摘要： We study the effect of electron doping on the bonding character and stability of two-dimensional (2D) structures of elemental boron, called borophene, which is known to form many stable allotropes. Our ab initio calculations for the neutral system reveal previously unknown stable 2D ε-B and ω-B structures. We find that the chemical bonding characteristic in this and other boron structures is strongly affected by extra charge. Beyond a critical degree of electron doping, the most stable allotrope changes from ε-B to a buckled honeycomb structure. Additional electron doping, mimicking a transformation of boron to carbon, causes a gradual decrease in the degree of buckling of the honeycomb lattice that can be interpreted as piezoelectric response. Net electron doping can be achieved by placing borophene in direct contact with layered electrides such as Ca2N. We find that electron doping can be doubled by changing from the B/Ca2N bilayer to the Ca2N/B/Ca2N sandwich geometry.
关键词： doping,boron,2D,ab initio calculation,structural stability,electronic structure
更新于2025-09-19 17:15:36
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Dipole Moment and Electronic Structure Calculations of the Electronic States of the Molecule SiC below 97000cm-1
摘要： Beside its importance in the astrophysics, the silicon carbide has a great importance in the industry of semiconductors and ceramics. Because of the absence of theoretical data, extensive ab initio calculations of dipole moment and higher excited electronic state have been done for this molecule. These calculations have been performed by using the Complete Active Space Self Consistent Field (CASSCF) with Multireference Configuration Interaction MRCI+Q (singly and doubly excitation with Davidson corrections). The potential energy and the dipole moment curves for the 47 low-lying singlet, triplet and quintet electronic states in the representation 2s+1Λ(+/-) of the molecule SiC have been calculated. The harmonic frequency ωe, the internuclear distance Re, the electronic energy with respect to the ground state Te, the rotational constants Be and the permanent dipole moment have been obtained for these electronic states. The comparison between the values of the present work and those available in the literature, for several electronic states, shows a good agreement. In the present work thirteen new electronic states have been investigated here for the first time. These new results may leads to more investigation of new experimental works on this molecule.
关键词： electronic structure,spectroscopic constants,permanent dipole moments,potential energy curves,ab initio calculation
更新于2025-09-09 09:28:46
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Electronic, bonding and optical properties of the LiGaGe2X6 (X?=?S, Se, and Te) compounds: An ab initio study
摘要： In order to gain an insight into the bonding and to characterize linear and nonlinear optical properties of three infrared LiGaGe2S6, LiGaGe2Se6, and LiGaGe2Te6 compounds, we performed an ab initio calculation based on density functional theory. The calculations determined lattice parameters, band gaps, dipole moments, and second harmonic components that commonly agreed well with the available experimental data. We show in this article, through a large body of calculations, the trend in the row of participating anions, S ? Se ? Te, enhances the polarization effect and the coordination structure distortions in the polyhedra groups forming the bonding pattern of the cell. This one also affects both the electronic and the optical properties, making the compounds more propitious for device-based optical applications.
关键词： Ab initio calculation,Bonding analysis,Optical properties,Electronic population
更新于2025-09-09 09:28:46
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Electronic Structure and Dipole Moment Calculations of the Electronic States of the Molecule ZnS
摘要： In this study, the low lying electronic states and spectroscopy of diatomic molecule ZnS in addition to its dipole moments have been investigated by performing highly correlated ab initio calculations, the Complete Active Space Self Consistent Field (CASSCF) method with Multi Reference Configuration Interaction (MRCI+Q) for an accurate picture for these states. The proposed study includes information about the potential energy curves of the lowest 12 singlet and 9 triplet electronic states of the molecule ZnS, in the representation 2s+1Λ(+/-). Nine of these states have been studied here for the first time. The harmonic frequency we, the internuclear distance re, the electronic energy with respect to the ground state Te, the rotational constant Be, and the permanent dipole moment μ have been calculated, compared and compiled with the available existing data to illustrate the electronic characteristics. The comparison of these values reveals a very good agreement.
关键词： potential energy curves,ab initio calculation,spectroscopic constants,electronic structure,dipole moments
更新于2025-09-04 15:30:14
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Superbound Excitons in 2D Phosphorene Oxides
摘要： The optical excitations in layered phosphorene oxides are studied via ab initio calculation together with GW approximation for the self-energy and solving the Bethe–Salpeter equation (BSE) for the excitations. It is found that the electronic structure of phosphorene oxides closely depend on the oxygen concentration, for the high oxygen coverage structure P4O10, it shows a strong localized molecular like electronic structure with exciton binding (Eb) energy up to 3.0 eV, which is several times larger than the ordinary Eb value in various low dimensional materials. This study may provide an alternative way to design functional layered materials with large exciton binding energy by controlling the oxidation level in phosphorene oxides.
关键词： GW approximation,exciton binding energy,Bethe–Salpeter equation,ab initio calculation,phosphorene oxides
更新于2025-09-04 15:30:14