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Author: Armin Taheri Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
The main objective of this thesis is to study phonon thermal transport in two-dimensional (2D) materials using first-principles density functional theory (DFT) calculations and the full solution of the Boltzmann transport equation (BTE). A wide range of 2D materials including graphene, 2D structures of group-VA, and recently emerged NX (X=P, As, Sb) compound monolayers are considered. Special attention is given to a mode-by-mode study of the thermal tunability via strain and functionalization. First, this thesis investigated the sensitivity of the DFT-calculated intrinsic thermal conductivity and phonon properties of 2D materials to the choice of exchange-correlation (XC) and pseudopotential (PP). It was found that the choice of the XC-PP combination results in significant discrepancies among predicted thermal conductivities of graphene at room temperature, in the range of 5442-8677 Wm^(-1)K^(-1). The LDA-NC and PBE-PAW combinations predicted the thermal conductivities in best agreement with available experimental data. This sensitivity analysis was an essential first step towards using DFT to engineer the phonon thermal transport in 2D systems. Next, DFT was used to systematically investigate the strain-dependent lattice thermal conductivity of -arsenene and -phosphorene, 2D monolayers of group-VA. The results showed that the thermal conductivity in both monolayers exhibits an up-and-down behavior when biaxial tensile strain is applied in the range from 0% to 9%. An interplay between phonon group velocities, heat capacities, and relaxation times, is found to be responsible for this behaviour. Finally, this project investigated the thermal conductivity of nitrogen functionalized - NX (X=P, As, Sb) monolayers. The results showed that the room-temperature thermal conductivities of -NP, -NAs, and -NSb are about 1.1, 5.5, and 34.0 times higher than those of their single-element -P, -As, and -Sb monolayers, respectively. The phonon transport analysis revealed that higher phonon group velocities, as well as higher phonon lifetimes were responsible for such an enhancement in the thermal conductivities of - NX compounds compared to single-element group-VA monolayers. Also, it was found that -NP has the minimum thermal conductivity among -NX monolayers, while it has the minimum average atomic mass. This thesis provides valuable insight into phonon physics and thermal transport in novel 2D materials using advanced DFT calculations.
Author: Armin Taheri Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
The main objective of this thesis is to study phonon thermal transport in two-dimensional (2D) materials using first-principles density functional theory (DFT) calculations and the full solution of the Boltzmann transport equation (BTE). A wide range of 2D materials including graphene, 2D structures of group-VA, and recently emerged NX (X=P, As, Sb) compound monolayers are considered. Special attention is given to a mode-by-mode study of the thermal tunability via strain and functionalization. First, this thesis investigated the sensitivity of the DFT-calculated intrinsic thermal conductivity and phonon properties of 2D materials to the choice of exchange-correlation (XC) and pseudopotential (PP). It was found that the choice of the XC-PP combination results in significant discrepancies among predicted thermal conductivities of graphene at room temperature, in the range of 5442-8677 Wm^(-1)K^(-1). The LDA-NC and PBE-PAW combinations predicted the thermal conductivities in best agreement with available experimental data. This sensitivity analysis was an essential first step towards using DFT to engineer the phonon thermal transport in 2D systems. Next, DFT was used to systematically investigate the strain-dependent lattice thermal conductivity of -arsenene and -phosphorene, 2D monolayers of group-VA. The results showed that the thermal conductivity in both monolayers exhibits an up-and-down behavior when biaxial tensile strain is applied in the range from 0% to 9%. An interplay between phonon group velocities, heat capacities, and relaxation times, is found to be responsible for this behaviour. Finally, this project investigated the thermal conductivity of nitrogen functionalized - NX (X=P, As, Sb) monolayers. The results showed that the room-temperature thermal conductivities of -NP, -NAs, and -NSb are about 1.1, 5.5, and 34.0 times higher than those of their single-element -P, -As, and -Sb monolayers, respectively. The phonon transport analysis revealed that higher phonon group velocities, as well as higher phonon lifetimes were responsible for such an enhancement in the thermal conductivities of - NX compounds compared to single-element group-VA monolayers. Also, it was found that -NP has the minimum thermal conductivity among -NX monolayers, while it has the minimum average atomic mass. This thesis provides valuable insight into phonon physics and thermal transport in novel 2D materials using advanced DFT calculations.
Author: Eui-Hyeok Yang Publisher: Elsevier ISBN: 0128184760 Category : Technology & Engineering Languages : en Pages : 502
Book Description
Synthesis, Modelling and Characterization of 2D Materials and Their Heterostructures provides a detailed discussion on the multiscale computational approach surrounding atomic, molecular and atomic-informed continuum models. In addition to a detailed theoretical description, this book provides example problems, sample code/script, and a discussion on how theoretical analysis provides insight into optimal experimental design. Furthermore, the book addresses the growth mechanism of these 2D materials, the formation of defects, and different lattice mismatch and interlayer interactions. Sections cover direct band gap, Raman scattering, extraordinary strong light matter interaction, layer dependent photoluminescence, and other physical properties. Explains multiscale computational techniques, from atomic to continuum scale, covering different time and length scales Provides fundamental theoretical insights, example problems, sample code and exercise problems Outlines major characterization and synthesis methods for different types of 2D materials
Author: Carlos Manuel Da Silva Leal Publisher: ISBN: Category : Languages : en Pages :
Book Description
Over the last decade, substantial attention has been paid to novel nanostructures based on two-dimensional (2D) materials. Among the hundreds of 2D materials that have been successfully synthesized in recent years, graphene, boron nitride, and molybdenum disulfide are the ones that have been intensively studied. It has been demonstrated that these materials exhibit thermal conductivities significantly higher than those of bulk samples of the same material. However, little is known about the physics of phonons in these materials, especially when tensile strain is applied. Properties of these materials are still not well understood, and modelling approaches are still needed to support engineering design of these novel nanostructures. In this thesis, I use state-of-the-art atomistic simulation techniques in combination with statistical thermodynamics formulations to obtain the phonon properties (lifetime, group velocity, and heat capacity) and thermal conductivities of unstrained and strained samples of graphene, boron nitride, molybdenum disulfide, and also superlattices of graphene and boron nitride. Special emphasis is given to the role of the acoustic phonon modes and the thermal response of these materials to the application of tensile strain. I apply spectral analysis to a set of molecular dynamics trajectories to estimate phonon lifetimes, harmonic lattice dynamics to estimate phonon group velocities, and Bose-Einstein statistics to estimate phonon heat capacities. These phonon properties are used to predict the thermal conductivity by means of a mode-dependent equation from kinetic theory. In the superlattices, I study the variation of the frequency dependence of the phonon properties with the periodicity and interface configuration (zigzag and armchair) for superlattices with period lengths within the coherent regime. The results showed that the thermal conductivity decreases significantly from the shortest period length to the second period length, 13% across the interfaces and 16% along the interfaces. For greater periods, the conductivity across the interfaces continues decreasing at a smaller rate of 11 W/mK per period length increase, driven by changes in the phonon group velocities (coherent effects). In contrast, the conductivity along the interfaces slightly recovers at a rate of 2 W/mK per period, driven by changes in the phonon relaxation times (diffusive effects).
Author: San-Dong Guo Publisher: Frontiers Media SA ISBN: 2832531636 Category : Science Languages : en Pages : 114
Book Description
The fascinating two-dimensional (2D) materials are being unconsciously applied in various fields from science to engineering, which is benefited from the glamorous physical and chemical properties of mechanics, optics, electronics, and magnetism. The representative 2D thermoelectric/piezoelectric materials can directly convert thermal/mechanical energy into electrical energy, which can resolve the energy issues and avoid further environmental deterioration. The thermoelectric or piezoelectric properties of various 2D materials, such as graphene, hexagonal boron nitride, black phosphorus, transition metal dichalcogenides (TMDs), arsenene, metal carbides and nitrides (MXenes), and so on, have been investigated in detail. Although tremendous progress has been achieved in the past few years, these properties still need to be improved for their practical application by designing new 2D materials, strain engineering, chemical functionalization, etc. In addition to this, in 2D materials, there are many other novel physical properties, such as magnetism, topology, valley, and so on. The combination of thermoelectricity/piezoelectricity with other unique properties may lead to novel device applications or scientific breakthroughs in new physics. Overall, the emergence of 2D thermoelectric and piezoelectric materials has expanded energy conversion research dramatically. By combing this new device concept with the novel 2D materials, original devices should have potential applications in energy harvesting.
Author: Zongyu Huang Publisher: CRC Press ISBN: 1000562824 Category : Science Languages : en Pages : 195
Book Description
Monoelemental 2D materials called Xenes have a graphene-like structure, intra-layer covalent bond, and weak van der Waals forces between layers. Materials composed of different groups of elements have different structures and rich properties, making Xenes materials a potential candidate for the next generation of 2D materials. 2D Monoelemental Materials (Xenes) and Related Technologies: Beyond Graphene describes the structure, properties, and applications of Xenes by classification and section. The first section covers the structure and classification of single-element 2D materials, according to the different main groups of monoelemental materials of different components and includes the properties and applications with detailed description. The second section discusses the structure, properties, and applications of advanced 2D Xenes materials, which are composed of heterogeneous structures, produced by defects, and regulated by the field. Features include: Systematically detailed single element materials according to the main groups of the constituent elements Classification of the most effective and widely studied 2D Xenes materials Expounding upon changes in properties and improvements in applications by different regulation mechanisms Discussion of the significance of 2D single-element materials where structural characteristics are closely combined with different preparation methods and the relevant theoretical properties complement each other with practical applications Aimed at researchers and advanced students in materials science and engineering, this book offers a broad view of current knowledge in the emerging and promising field of 2D monoelemental materials.
Author: Yatish T. Shah Publisher: CRC Press ISBN: 1315305933 Category : Technology & Engineering Languages : en Pages : 1112
Book Description
The book details sources of thermal energy, methods of capture, and applications. It describes the basics of thermal energy, including measuring thermal energy, laws of thermodynamics that govern its use and transformation, modes of thermal energy, conventional processes, devices and materials, and the methods by which it is transferred. It covers 8 sources of thermal energy: combustion, fusion (solar) fission (nuclear), geothermal, microwave, plasma, waste heat, and thermal energy storage. In each case, the methods of production and capture and its uses are described in detail. It also discusses novel processes and devices used to improve transfer and transformation processes.
Author: Alexander I. Zhmakin Publisher: Springer Nature ISBN: 3031259734 Category : Science Languages : en Pages : 419
Book Description
This book presents a broad and well-structured overview of various non-Fourier heat conduction models. The classical Fourier heat conduction model is valid for most macroscopic problems. However, it fails when the wave nature of the heat propagation becomes dominant and memory or non-local spatial effects become significant; e.g., during ultrafast heating, heat transfer at the nanoscale, in granular and porous materials, at extremely high values of the heat flux, or in heat transfer in biological tissues. The book looks at numerous non-Fourier heat conduction models that incorporate time non-locality for materials with memory, such as hereditary materials, including fractional hereditary materials, and/or spatial non-locality, i.e. materials with a non-homogeneous inner structure. Beginning with an introduction to classical transport theory, including phase-lag, phonon, and thermomass models, the book then looks at various aspects of relativistic and quantum transport, including approaches based on the Landauer formalism as well as the Green-Kubo theory of linear response. Featuring an appendix that provides an introduction to methods in fractional calculus, this book is a valuable resource for any researcher interested in theoretical and numerical aspects of complex, non-trivial heat conduction problems.
Author: Detlef Bahnemann Publisher: Springer Nature ISBN: 3030637131 Category : Science Languages : en Pages : 1914
Book Description
The handbook comprehensively covers the field of inorganic photochemistry from the fundamentals to the main applications. The first section of the book describes the historical development of inorganic photochemistry, along with the fundamentals related to this multidisciplinary scientific field. The main experimental techniques employed in state-of-art studies are described in detail in the second section followed by a third section including theoretical investigations in the field. In the next three sections, the photophysical and photochemical properties of coordination compounds, supramolecular systems and inorganic semiconductors are summarized by experts on these materials. Finally, the application of photoactive inorganic compounds in key sectors of our society is highlighted. The sections cover applications in bioimaging and sensing, drug delivery and cancer therapy, solar energy conversion to electricity and fuels, organic synthesis, environmental remediation and optoelectronics among others. The chapters provide a concise overview of the main achievements in the recent years and highlight the challenges for future research. This handbook offers a unique compilation for practitioners of inorganic photochemistry in both industry and academia.
Author: Armin Taheri
Author: Armin Taheri
Author: Eui-Hyeok Yang
Author: Carlos Manuel Da Silva Leal
Author: Guangzhao Wang
Author: San-Dong Guo
Author: Daniel P. Sellan
Author: Zongyu Huang
Author: Yatish T. Shah
Author: Alexander I. Zhmakin
Author: Detlef Bahnemann