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SSRN 2023年

作者： Shah, Vaishali Kshirsagar, Bhakti Mandalia, Raviraj Pujari, Bhalchandra Premkumar, S. Department of Scientific Computing Modeling and Simulation Savitribai Phule Pune University Maharashtra Pune411007 India Department of Physics Savitribai Phule Pune University Maharashtra Pune411007 India Armament Research and Development Establishment Maharashtra Pune411021 India

Can a material be designed and engineered to use as a replacement for anenvironmentally unfriendly material? In the specific context of lead titanates, the quest for finding such material replacements is ongoing, beginning from lead free alternatives with simple perovskite compositions, extending to hybrid and double perovskite compositions. In this work, we have demonstrated through ab initio density functional theory investigations the tunability of multiple properties of a simple perovskite Ba0.5Sn0.5TiO3 to mimic that of PbTiO3. Our results show that A-site Sn enhances the polarization of Ba0.5Sn0.5TiO3 closer to that of PbTiO3 and tunes its pressure dependent polarization behavior to become similar to that of PbTiO3 and dissimilar to that of BaTiO3 by reorienting the displacements profiles of A, B site and O atoms to become like that of their counterparts in PbTiO3. Compressive pressures facilitate transition from indirect to direct bandgap, increase the mobility of charge carriers and lead to stronger exciton binding in Ba0.5Sn0.5TiO3 opening up its use for optoelectronics. Ba0.5Sn0.5TiO3 has an early onset of absorption and its absorption spectra in UV range is qualitatively similar to PbTiO3 albeit with reduced absorption peak heights and broadening. The absorption spectra of Ba0.5Sn0.5TiO3 can be modified via application of strains and peak absorption heights can be changed to become similar to that of PbTiO3. We also demonstrate that the dielectric constant as well as refractive index of Ba0.5Sn0.5TiO3 can be modulated to increase (decrease) by applying compressive (tensile) strains. The study of mechanical properties demonstrates that Ba0.5Sn0.5TiO3 is more ductile and is mechanically stable even under higher compressive strains, making it excitingly attractive for device applications over other lead-free alternatives that are known to display poor stabilities. These comprehensive investigations demonstrate for the first time that all the physical propert

关键词： Polarization

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Electron-phonon interaction contribution to the total energy of group IV semiconductor polymorphs: Evaluation and implications

arXiv

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arXiv 2022年

作者： Varma, Arjun Varma Ramasimha Paul, Shilpa Itale, Anup Pable, Pranav Tibrewala, Radhika Dodal, Samruddhi Yerunkar, Harshal Bhaumik, Saurav Shah, Vaishali Gururajan, Mogadalai Pandurangan Prasanna, Tiramkudlu R.S. Department of Metallurgical Engineering and Materials Science Indian Institute of Technology Bombay Mumbai400076 India Department of Mathematics Indian Institute of Technology Bombay Mumbai400076 India Department of Scientific Computing Modeling and Simulation Savitribai Phule Pune University Pune411007 India

In density functional theory (DFT) based total energy studies, the van der Waals (vdW) and zero-point vibrational energy (ZPVE) correction terms are included to obtain energy differences between polymorphs. We propose and compute a new correction term to the total energy, due to electron-phonon interactions (EPI). We rely on Allen's general formalism, which goes beyond the Quasi-Harmonic Approximation (QHA), to include the free energy contributions due to quasiparticle interactions. We show that, for semiconductors and insulators, the EPI contributions to the free energies of electrons and phonons are the corresponding zero-point energy contributions. Using an approximate version of Allen's formalism in combination with the Allen-Heine theory for EPI corrections, we calculate the zero-point EPI corrections to the total energy for cubic and hexagonal polytypes of Carbon, Silicon and Silicon Carbide. The EPI corrections alter the energy differences between polytypes. In SiC polytypes, the EPI correction term is more sensitive to crystal structure than the vdW and ZPVE terms and is thus essential in determining their energy differences. It clearly establishes that the cubic SiC-3C is metastable and hexagonal SiC-4H is the stable polytype. Our results are consistent with the experimental results of Kleykamp. Our study enables the inclusion of EPI corrections as a separate term in the free energy expression. This opens the way to go beyond the QHA by including the contribution of EPI on all thermodynamic properties. © 2022, CC BY.

关键词： Silicon carbide

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Site-independent strong phonon-vacancy scattering in high-temperature ceramics ZrB2 and HfB2

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Physical Review Materials 2022年第6期6卷 065403-065403页

作者： Vrishali Sonar Rohan Dehankar K. P. Vijayalakshmi Natalio Mingo Ankita Katre Department of Scientific Computing Modeling and Simulation SP Pune University Pune 411007 India Department of Physics Adam Mickiewicz University 61-614 Poznàn Poland Vikram Sarabhai Space Centre Kochuveli Thiruvananthapuram 695022 India Université Grenoble Alpes CEA LITEN 17 rue des Martyrs 38054 Grenoble Cedex 9 France

Similar effects of metal and boron vacancies on phonon scattering and lattice thermal conductivity (κl) of ZrB2 and HfB2 are reported. These defects challenge the conventional understanding that associates larger impacts to bigger defects. We find the underlying reason to be a strong local perturbation caused by boron vacancy that substantially changes the interatomic force constants. In contrast, a long ranged but weaker perturbation is seen in the case of metal vacancy. We show that these behaviors originate from a mixed metallic and covalent bonding nature in the metal diborides. The thermal transport calculations are performed in a complete ab initio framework based on Boltzmann transport equation and density functional theory. Phonon-vacancy scattering is calculated using ab initio Green's function approach. Effects of natural isotopes and grain boundaries on κl are also systematically investigated, however we find an influential role of vacancies to explain large variations seen in the experiments. We further report a two-order of magnitude difference between the amorphous and pure-crystal limits. Our results outline significant material design aspects for these multifunctional high-temperature ceramics.

关键词： Crystal defects Phonons Thermal conductivity Ab initio calculations Green's function methods

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New Two-Dimensional Gallenene Monolayer for Na-Ion Batteries and Electrocatalysis

SSRN

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SSRN 2023年

作者： Ubaid, Mohammad Bhamu, K.C. Kang, Sung Gu Aziz, Anver Pujari, Bhalchandra S. Department of Physics Jamia Millia Islamia New Delhi110025 India School of Chemical Engineering University of Ulsan Daehak-ro 93 Nam-gu Ulsan44610 Korea Republic of Department of Scientific Computing Modeling & Simulation Savitribai Phule Pune University Pune411007 India

Alkali metal Na-based batteries offer eco-friendly and low-cost alternatives of lithium-ion batteries (LIBs). However, the relative scarsity of a high-performance anode restricts the development of Na-ion batteries (NIBs). Herein, we theoretically explore the potential applications of a new elemental 2D monolayer of gallium, gallenene (Ga100-ML) as anode materials for Na-ion batteries and electrocatalysis towrads hydrogen evolution reaction (HER). It is found that the Ga100ML is energetically, dynamically, and mechanically stable. We observe that the Ga100-ML is metallic and a maximum of 45 Na atoms can be inserted into it providing a sufficiently high theoretical storage capacity of 961.30 mAh/g and a low diffusion barrier of 0.36 eV. Further, our data suggest that Pt decorated Ga100-ML exhibits excellent catalytic activity for HER with a minimum hydrogen adsorption Gibbs free energy of -0.12 eV. Our findings suggest that these results could be beneficial for designing anode materials for Na-ion batteries and electrocatalysis for HER. © 2023, The Authors. All rights reserved.

关键词： Free energy

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Structure of the Liquid-Vacuum Interface of Room-Temperature Ionic Liquids:A Molecular Dynamics Study

Structure of the Liquid-Vacuum Interface of Room-Temperature...

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The International Conference on Theory and Applications of Computational Chemistry 2008(2008理论与计算机化学国际会议)

作者： Shu Wang Shu Li Lei Liu Tianying Yan Xueping Gao G.A.Voth Institute of Scientific Computing Nankai UniversityTianjin 300071China Center for Biophysical Modeling and Simulation and Department of ChemistryUniversity of Utah Salt Lake CityUT 84112-0850 College of Chemistry Nankai UniversityTianjin 300071China College of ChemistryNankai UniversityTianjin 300071China

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First-principles determination of the phonon-point defect scattering and thermal transport due to fission products in ThO2

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Physical Review Materials 2024年第2期8卷 025401-025401页

作者： Linu Malakkal Ankita Katre Shuxiang Zhou Chao Jiang David H. Hurley Chris A. Marianetti Marat Khafizov Computational Mechanics and Materials Department Idaho National Laboratory Idaho Falls Idaho 83415 USA Department of Scientific Computing Modeling and Simulation SP Pune University Pune 411007 India Idaho National Laboratory Idaho Falls Idaho 83415 USA Department of Applied Physics and Applied Mathematics Columbia University 500 West 120th Street New York New York 10027 USA Department of Mechanical and Aerospace Engineering The Ohio State University 201 West 19th Avenue Columbus Ohio 43210 USA

This work presents the first-principles calculations of the lattice thermal conductivity degradation due to point defects in thorium dioxide using an iterative solution of the Peierls-Boltzmann transport equation. We have used the nonperturbative Green's function methodology to compute the phonon-point defect scattering rates that consider the local distortion around the point defect, including the mass difference changes, interatomic force constants, and structural relaxation near the point defects. The point defects considered in this work include the vacancy of thorium (VTh) and oxygen (VO), substitutions of helium (HeTh), krypton (KrTh), zirconium (ZrTh), iodine (ITh), and xenon (XeTh) in the thorium site, and the three different configurations of the Schottky defects. The results of the phonon-defect scattering rate reveal that among all the considered intrinsic defects, the thorium vacancy and helium substitution in the thorium site scatter the phonon most due to the substantial changes in the force constant and structural distortions. The scattering of phonons due to the substitutional defects unveils that the zirconium atom scatters phonons the least, followed by xenon, iodine, krypton, and helium. This is contrary to the intuition that the scattering strength follows HeTh>KrTh>ZrTh>ITh>XeTh based on the mass difference. This striking difference in the zirconium phonon scattering is due to the local chemical environment changes. Zirconium is an electropositive element with valency similar to thorium and, therefore, can bond with the oxygen atoms, thus creating less force constant variance compared to iodine, an electronegative element, and the noble gases helium, xenon, and krypton. These results can serve as a benchmark for analytical models and help the engineering-scale modeling effort for nuclear design.

关键词： Carrier dynamics Energy materials Heat transfer Irradiation effects Lattice dynamics Nuclear power Phonons Thermal conductivity Thermal properties

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Site independent strong phonon-vacancy scattering in high temperature ceramics ZrB2and HfB2

arXiv

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arXiv 2022年

作者： Sonar, Vrishali Dehankar, Rohan Vijayalakshmi, K.P. Mingo, Natalio Katre, Ankita Department of Scientific Computing Modeling and Simulation SP Pune University Pune411007 India Dept. of Physics Adam Mickiewicz University Poznàn61-614 Poland Vikram Sarabhai Space Centre Kochuveli Thiruvananthapuram695022 India Université Grenoble Alpes CEA LITEN 17 rue des Martyrs Grenoble Cedex 938054 France

Similar effects of metal and boron vacancies on phonon scattering and lattice thermal conductivity (κl) of ZrB2and HfB2are reported. These defects challenge the conventional understanding that associates larger impacts to bigger defects. We find the underlying reason to be a strong local perturbation caused by the boron vacancy that substantially changes the interatomic force constants. In contrast, a long ranged but weaker perturbation is seen in the case metal vacancies. We show that these behaviours originate from a mixed metallic and covalent bonding nature in the metal diborides. The thermal transport calculations are performed in a complete ab initio framework based on Boltzmann transport equation and density functional theory. Phonon-vacancy scattering is calculated using ab initio Green's function approach. Effects of natural isotopes and grain boundaries on κlare also systematically investigated, however we find an influential role of vacancies to explain large variations seen in the experiments. We further report a two-order of magnitude difference between the amorphous and pure-crystal limits. Our results outline significant material design aspects for these multi-functional high temperature ceramics. © 2022, CC BY-NC-ND.

关键词： Phonons

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MICROSIM: A high performance phase-field solver based on CPU and GPU implementations

arXiv

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arXiv 2024年

作者： Dutta, Tanmay Mohan, Dasari Shenoy, Saurav Attar, Nasir Kalokhe, Abhikshek Sagar, Ajay Bhure, Swapnil Pradhan, Swaroop S. Praharaj, Jitendriya Mridha, Subham Kushwaha, Anshika Shah, Vaishali Gururajan, M.P. Shenoi, V. Venkatesh Phanikumar, Gandham Bhattacharyya, Saswata Choudhury, Abhik Department of Materials Engineering Indian Institute of Science Karnataka Bangalore560012 India Department of Metallurgical and Materials Engineering IIT Madras Tamil Nadu Chennai600036 India Department of Materials Science and Metallurgical Engineering IIT Hyderabad Telangana Hyderabad502284 India Center for development of Advanced Computing Pune University Campus Maharashtra Pune411007 India Department of Metallurgical Engineering and Materials Science IIT Bombay Powai Maharashtra Mumbai400076 India Department of Scientific Computing Modeling and Simulation Savitribai Phule Pune University Maharashtra Pune411007 India

The phase-field method has become a useful tool for the simulation of classical metallurgical phase transformations as well as other phenomena related to materials science. The thermodynamic consistency that forms the basis of these formulations lends to its strong predictive capabilities and utility. However, a strong impediment to the usage of the method for typical applied problems of industrial and academic relevance is the significant overhead with regard to the code development and know-how required for quantitative model formulations. In this paper, we report the development of an open-source phase-field software stack that contains generic formulations for the simulation of multi-phase and multi-component phase transformations. The solvers incorporate thermodynamic coupling that allows the realization of simulations with real alloys in scenarios directly relevant to the materials industry. Further, the solvers utilize parallelization strategies using either multiple CPUs or GPUs to provide cross-platform portability and usability on available supercomputing machines. Finally, the solver stack also contains a graphical user interface to gradually introduce the usage of the software. The user interface also provides a collection of post-processing tools that allow the estimation of useful metrics related to microstructural evolution. © 2024, CC BY-NC-SA.

关键词： Technology transfer

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Experimental and Theoretical Evidence of Novel 2d Β-Nis Nanostructures Based High-Performance Battery-Type Solid-State Supercapacitor

SSRN

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SSRN 2023年

作者： Singh, Diwakar Samtham, Manopriya Bisht, Neeta Choudhary, Ekta Kumar, Vikesh Jangir, Ravindra Sonnathi, Neeleshwar Hosmani, Santosh S. Katre, Ankita Devan, Rupesh S. Department of Metallurgy Engineering and Materials Science Indian Institute of Technology Indore Simrol Khandwa Road Indore453552 India Department of Scientific Computing Modeling and Simulation Savitribai Phule Pune University Pune411007 India University School of Basic and Applied Sciences Guru Gobind Singh Indraprastha University Delhi110078 India Accelerator Physics and Synchrotrons Utilization Division Raja Ramanna Centre for Advanced Technology Indore452013 India

Recently, quirky features and eccentric structures of transition metal sulfides have grasped great attention to remove roadblocks and unwrap fresh avenues for electrodes in energy storage devices. Herein, we developed a 2D beta phase nickel sulfide nanosheets (2D β-NiS NSs) electrode with remarkable enhancement in charge storage properties. When served as active electrode for electrochemical tests, 2D NiS NSs exhibited ultra-high capacitance of 2693 F/g at 1 mV/s and specific capacity of 219 mAh/g at 1A/g. The symmetric battery type solid-state supercapacitor device comprising 2D β-NiS NSs electrodes exhibits specific capacity of 83.43 mAh/g at 2 A/g over broad potential range of 0.7V with good cycling performance, and energy and power density of 28.9 Wh/kg (@ 2A/g) and 21 kW/kg (@ 6A/g), respectively. Complementary first-principles density functional theory (DFT) calculations accomplished to explore the electrolyte ion interactions with nickel sulfide nanostructures defining 2D NiS NSs as a potential candidate for real-time applications. © 2023, The Authors. All rights reserved.

关键词： Sulfur compounds

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First-principles determination of the phonon-point defect scattering and thermal transport due to fission products in ThO2

arXiv

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arXiv 2023年

作者： Malakkal, Linu Katre, Ankita Zhou, Shuxiang Jiang, Chao Hurley, David H. Marianetti, Chris A. Khafizov, Marat Computational Mechanics and Materials Department Idaho National Laboratory Idaho FallsID83415 United States Department of Scientific Computing Modeling and Simulation SP Pune University Pune411007 India Idaho National Laboratory Idaho FallsID83415 United States Department of Applied Physics and Applied Mathematics Columbia University 500 West 120th Street New YorkNY10027 United States Department of Mechanical and Aerospace Engineering The Ohio State University 201 West 19th Ave ColumbusOH43210 United States

This work presents the first-principles calculations of the lattice thermal conductivity degradation due to point defects in thorium dioxide using an iterative solution of the Peirels-Boltzmann transport equation. We have used the non-perturbative Green's function methodology to compute the phononpoint defect scattering rates that consider the local distortion around the point defect, including the mass difference changes, interatomic force constants, and structural relaxation near the point defects. The point defects considered in this work include the vacancy of thorium (VTh) and oxygen (VO), substitutions of helium (HeTh), krypton (KrTh), zirconium (ZrTh), iodine (ITh) and xenon (XeTh) in the thorium site, and the three different configurations of the Schottky defects. The results of the phonon-defect scattering rate reveal that, among all the considered intrinsic defects, the thorium vacancy and helium substitution in the thorium site scatter the phonon most due to the substantial changes in the force constant and structural distortions. The scattering of phonons due to the substitutional defects unveils that the zirconium atom scatters phonons the least, followed by xenon, iodine, krypton, and helium. This is contrary to the intuition that the scattering strength follows HeTh > KrTh > ZrTh > ITh > XeTh based on the mass difference. This striking difference in the zirconium phonon scattering is due to the local chemical environment changes. Zirconium is an electropositive element with valency similar to thorium and, therefore, can bond with the oxygen atoms, thus creating less force constant variance compared to iodine, an electronegative element, and the noble gases helium, xenon, and krypton. These results can serve as a benchmark for analytical models and help the engineering-scale modeling effort for nuclear design. © 2023, CC BY.

关键词： Boltzmann equation

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