 Subjects -> ELECTRONICS (Total: 207 journals)
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- In-situ topotactic chemical reaction for spectroscopies
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Authors: Tappei Kawakami; Kosuke Nakayama, Katsuaki Sugawara Takafumi Sato
First page: 033001
Abstract: Topotactic chemical reaction (TCR) is a chemical process that transforms one crystalline phase to another while maintaining one or more of the original structural frameworks, typically induced by the local insertion, removal, or replacement of atoms in a crystal. The utilization of TCR in atomic-layer materials and surfaces of bulk crystals leads to exotic quantum phases, as highlighted by the control of topological phases, the emergence of two-dimensional (2D) superconductivity, and the realization of 2D ferromagnetism. Advanced surface-sensitive spectroscopies such as angle-resolved photoemission spectroscopy and scanning tunneling microscopy are leading techniques to visualize the electronic structure of such exotic states and provide us a guide to further functionalize material properties. In this review article, we summarize the recent progress in this field, with particular emphasis on intriguing results obtained by combining spectroscopies and TCR in thin films.
Citation: Electronic Structure
PubDate: 2024-07-01T23:00:00Z
DOI: 10.1088/2516-1075/ad5acb
Issue No: Vol. 6, No. 3 (2024)
- Halide perovskites from first principles: from fundamental optoelectronic
properties to the impact of structural and chemical heterogeneity-
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Authors: Marina R Filip; Linn Leppert
First page: 033002
Abstract: Organic-inorganic metal-halide perovskite semiconductors have outstanding and widely tunable optoelectronic properties suited for a broad variety of applications. First-principles numerical modelling techniques are playing a key role in unravelling structure-property relationships of this structurally and chemically diverse family of materials, and for predicting new materials and properties. Herein we review first-principles calculations of the photophysics of halide perovskites with a focus on the band structures, optical absorption spectra and excitons, and the effects of electron- and exciton-phonon coupling and temperature on these properties. We focus on first-principles approaches based on density functional theory and Green’s function-based many-body perturbation theory and provide an overview of these approaches. While a large proportion of first-principles studies have been focusing on the prototypical ABX3 single perovskites based on Pb and Sn, recent years have witnessed significant efforts to further functionalize halide perovskites, broadening this family of materials to include double perovskites, quasi-low-dimensional structures, and other organic-inorganic materials, interfaces and heterostructures. While this enormous chemical space of perovskite and perovskite-like materials has only begun to be tapped experimentally, recent advances in theoretical and computational methods, as well as in computing infrastructure, have led to the possibility of understanding the photophysics of ever more complex systems. We illustrate this progress in our review by summarizing representative studies of first-principles calculations of halide perovskites with various degrees of complexity.
Citation: Electronic Structure
PubDate: 2024-07-21T23:00:00Z
DOI: 10.1088/2516-1075/ad5898
Issue No: Vol. 6, No. 3 (2024)
- A DFT insight of the electronic, thermodynamic, and thermoelectric
properties of RuO2-
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Authors: E Maskar; A Fakhim Lamrani, R Zosiamliana D P Rai
First page: 035001
Abstract: In this study, we explore the structural, electronic, thermodynamic, and thermoelectric properties of RuO2 using density functional theory. The derived equilibrium structural parameters agree with other theoretical and experimental results. The widely used modified Becke–Johnson (mBJ-GGA) potential is adopted for accurate electronic band gap estimation. To incorporate the effect of the extended orbital of the Ru atom, spin-orbit coupling has been used in combination with the mBJ potential. The investigation of electronic properties revealed an indirect semi-conducting nature with a band gap along the W-L symmetry. The calculated band gaps are 1.685 and 1.658 eV from mBJ and mBJ + SOC, respectively. The dynamical stability is tested and verified by calculating the phonon dispersion curve. We have employed the quasiharmonic approximation-based Gibbs2 package to determine the pressure and temperature-dependent thermodynamical parameters, such as cell volume, Debye temperature, heat capacity, entropy, and thermal expansion coefficient. This study uses the BoltzTraP simulation algorithm to determine the thermoelectric parameters such as the Seebeck coefficient, electrical conductivity, and thermal conductivity.
Citation: Electronic Structure
PubDate: 2024-07-02T23:00:00Z
DOI: 10.1088/2516-1075/ad5b33
Issue No: Vol. 6, No. 3 (2024)
- Doping dependence and multichannel mediators of superconductivity:
calculations for a cuprate model-
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Authors: Fabian Schrodi; Alex Aperis Peter M Oppeneer
First page: 035002
Abstract: We study two aspects of the superconductivity in a cuprate model system, its doping dependence and the influence of competing pairing mediators. We first include electron–phonon interactions beyond Migdal’s approximation and solve self-consistently, as a function of doping and for an isotropic electron–phonon coupling, the full-bandwidth, anisotropic vertex-corrected Eliashberg equations under a non-interacting state approximation for the vertex correction. Our results show that such pairing interaction supports the experimentally observed -wave symmetry of the superconducting gap, but only in a narrow doping interval of the hole-doped system. Depending on the coupling strength, we obtain realistic values for the gap magnitude and superconducting critical temperature close to optimal doping, rendering the electron–phonon mechanism an important candidate for mediating superconductivity in this model system. Second, for a doping near optimal hole doping, we study multichannel superconductivity, by including both vertex-corrected electron–phonon interaction and spin and charge fluctuations as pairing mechanisms. We find that both mechanisms cooperate to support an unconventional d-wave symmetry of the order parameter, yet the electron–phonon interaction is mainly responsible for the Cooper pairing and high critical temperature . Spin fluctuations are found to have a suppressing effect on the gap magnitude and critical temperature due to their repulsive interaction at small coupling wave vectors.
Citation: Electronic Structure
PubDate: 2024-07-10T23:00:00Z
DOI: 10.1088/2516-1075/ad5e29
Issue No: Vol. 6, No. 3 (2024)
- Approaching periodic systems in ensemble density functional theory via
finite one-dimensional models-
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Authors: Remi J Leano; Aurora Pribram-Jones David A Strubbe
First page: 035003
Abstract: Ensemble density functional theory (EDFT) is a generalization of ground-state DFT, which is based on an exact formal theory of finite collections of a system’s ground and excited states. EDFT in various forms has been shown to improve the accuracy of calculated energy level differences in isolated model systems, atoms, and molecules, but it is not yet clear how EDFT could be used to calculate band gaps for periodic systems. We extend the application of EDFT toward periodic systems by estimating the thermodynamic limit with increasingly large finite one-dimensional ‘particle in a box’ systems, which approach the uniform electron gas (UEG). Using ensemble-generalized Hartree and local spin density approximation exchange-correlation functionals, we find that corrections go to zero in the infinite limit, as expected for a metallic system. However, there is a correction to the effective mass, with results comparable to other calculations on 1D, 2D, and 3D UEGs, which indicates promise for non-trivial results from EDFT on periodic systems.
Citation: Electronic Structure
PubDate: 2024-07-18T23:00:00Z
DOI: 10.1088/2516-1075/ad610e
Issue No: Vol. 6, No. 3 (2024)
- Regulating electronic structure of anionic oxygen by Ti4+ doping to
stabilize layered Li-rich oxide cathodes for Li-ion batteries-
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Authors: Xinyu Zhu; Luqi Hao, Yongjian Li, Lai Chen, Qing Huang, Yun Lu, Ning Li Yuefeng Su
First page: 035004
Abstract: Layered Li-rich oxide cathodes enable to activate lattice oxygen anions redox in the charge compensation process and provide superior high specific capacity over 250 mAh g−1 due to their unique configuration, and thus attracting great attentions as promising cathode candidates for Li-ion batteries. However, how to better stabilize the bulk lattice oxygen framework and surface structure, and slow down the release of oxygen, is still major bottleneck to develop high performance Li-rich materials. Transition metal ions with outer d0 electronic configuration have distortable configuration, which can accommodate the local structure and chemical environment of the material, and then improve structural stability. Herein this work, the d0 transition metal Ti4+ is used as doping element to improve the chemical and structural stability, capacity retention and lithium ion diffusion kinetics of Li-rich material. The role of Ti in the material modification is revealed through synchrotron-based soft x-ray absorption spectroscopy, XRD, XPS and electrochemical tests. The improvement in structural stability can be attributed to that Ti doping can adjust the hybridization of O2p and TM3d to regulate the local electronic structure of both bulk lattice oxygen and surface oxygen vacancies. It is hoped that this work should shed light on the development of high-performance cathode materials for Li-ion Batteries.
Citation: Electronic Structure
PubDate: 2024-07-30T23:00:00Z
DOI: 10.1088/2516-1075/ad6386
Issue No: Vol. 6, No. 3 (2024)
- Self-similarity of quantum transport in graphene using electrostatic gate
and substrate-
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Authors: Mohammed Miniya; Luis M Gaggero-Sager, Miguel E Mora-Ramos, Rolando Pérez-Álvarez Outmane Oubram
First page: 035005
Abstract: A particular design for multibarrier structure in graphene, yielding a self-similar transport response, is proposed. The potential profile is based on rectangular wells and barriers, generated according independent nth order scaling laws for their heights and widths. The barriers are constructed by means of two distinct approaches (electrostatic or substrate). Dirac equation and transfer matrix approach are used to calculate transmission properties which, in turn, allow to evaluate the conductance via Landauer–Büttiker formalism. It is found that self-similarity with determined scaling rules between nth and th generations of transport properties appears when the order of generating laws is equal or greater than n = 7. Our proposal would be the first in which the self-similarity property is transferred from geometry to the spectrum, and consequently, to the transport properties of a quantum heterostructure. Possible ways of practical realization for the proposed structures are commented.
Citation: Electronic Structure
PubDate: 2024-08-20T23:00:00Z
DOI: 10.1088/2516-1075/ad6c96
Issue No: Vol. 6, No. 3 (2024)
- Ultrafast charge carrier dynamics of methylammonium lead iodide from first
principles-
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Authors: Ariel M Cabrera; Michele Guerrini, Henry P Pinto Caterina Cocchi
First page: 037001
Abstract: Methylammonium lead iodide (MAPbI3) has been a major focus of photovoltaic research for the last decade. The unique interplay between the structural and electronic properties of this material contributes to its exciting optical properties especially under the action of an ultrafast laser pulse. First-principles methods like real-time time-dependent density functional theory (RT-TDDFT) enable performing corresponding simulations without the aid of empirical parameters: the gained knowledge can be applied to future studies of other complex materials. In this work, we investigate the ultrafast charge-carrier dynamics and the nonlinear optical response of MAPbI3 excited by a resonant pulse above the gap. First, we examine the electronic and optical properties in the static regime. Next, we impinge the system with a femtosecond field of varying intensity and follow the evolution of the photoexcited carrier density. A pronounced intensity-dependent response is observed, manifested by high-harmonic generation and nonlinear trends in the number of excited electrons and excitation energy. Our results provide relevant indications about the behavior of MAPbI3 under strong and coherent radiation and confirm that RT-TDDFT is a viable tool to simulate the photo-induced dynamics of complex materials from first principles.
Citation: Electronic Structure
PubDate: 2024-07-04T23:00:00Z
DOI: 10.1088/2516-1075/ad5b40
Issue No: Vol. 6, No. 3 (2024)
- Amesp: Atomic and molecular electronic structure program
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Authors: Yingfeng Zhang
First page: 037002
Abstract: The atomic and molecular electronic structure program (Amesp) is a general-purpose electronic structure program designed for the study of molecular electronic structures. It incorporates a series of modern electronic structure methods, including Hartree–Fock, density functional theory, Multiconfigurational self-consistent field, Møller–Plesset, configuration-interaction, coupled-cluster, semiempirical methods, and molecular force fields. Amesp strives to offer an efficient and user-friendly tool specifically designed for computing for molecules ranging from small to complex biomolecules. In this paper, we highlight the features of Amesp and offer an overview.
Citation: Electronic Structure
PubDate: 2024-07-07T23:00:00Z
DOI: 10.1088/2516-1075/ad5cb5
Issue No: Vol. 6, No. 3 (2024)
- Facilities and practices for linear response Hubbard parameters U and J in
Abinit-
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Authors: Lórien MacEnulty; Matteo Giantomassi, Bernard Amadon, Gian-Marco Rignanese David D O’Regan
First page: 037003
Abstract: Members of the density functional theory (DFT)+U family of functionals are increasingly prevalent methods of addressing errors intrinsic to (semi-) local exchange-correlation functionals at minimum computational cost, but require their parameters U and J to be calculated in situ for a given system of interest, simulation scheme, and runtime parameters. The self-consistent field (SCF) linear response approach offers ab initio acquisition of the U and has recently been extended to compute the J analogously, which measures localized errors related to exchange-like effects. We introduce a renovated post-processor, the lrUJ utility, together with this detailed best-practices guide, to enable users of the popular, open-source Abinit first-principles simulation suite to engage easily with in situ Hubbard parameters and streamline their incorporation into material simulations of interest. Features of this utility, which may also interest users and developers of other DFT codes, include n-degree polynomial regression, error analysis, Python plotting facilities, didactic documentation, and avenues for further developments. In this technical introduction and guide, we place particular emphasis on the intricacies and potential pitfalls introduced by the projector augmented wave method, SCF mixing schemes, and non-linear response, several of which are translatable to DFT+U(+J) implementations in other packages.
Citation: Electronic Structure
PubDate: 2024-07-25T23:00:00Z
DOI: 10.1088/2516-1075/ad610f
Issue No: Vol. 6, No. 3 (2024)
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