Academic literature on the topic 'ELECTRONS; TWO-DIMENSIONAL CALCULATIONS; DYNAMICS'

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Journal articles on the topic "ELECTRONS; TWO-DIMENSIONAL CALCULATIONS; DYNAMICS"

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Filatov, Aleksandr Nikolaevich, and Vladimir Kuz'mich Shilov. "Radial dynamics of electrons in two-section linear accelerator." International Journal of Electrical and Computer Engineering (IJECE) 9, no. 1 (February 1, 2019): 215. http://dx.doi.org/10.11591/ijece.v9i1.pp215-220.

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This article discusses possibility of harness wiring with the use of focusing system of high frequency eigenfields of accelerating resonators in standing wave linear accelerators on the basis of biperiodic slowing systems. The scopes of business activities and specificity of existing engineering processes applied in industry, especially in chemistry and metallurgy, require for special measures on environmental protection. At present electron linear accelerators operating in pulse mode are used for application purposes. Such accelerators can be characterized by sufficient beam power for efficient industrial use and for environmental protection. The results of numerical analysis of electron dynamics in two-section accelerator upon various initial conditions are presented. The obtained results are applied for development of actual accelerator, calculated and experimental data are given. The performed experimental study confirmed possibility of development of standing wave linear accelerator without external magnetic focusing system with output beam diameter of not higher than . The results of calculations of beam dynamics are experimentally verified.
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Quintas-Sánchez, Ernesto, and Richard Dawes. "Spectroscopy and Scattering Studies Using Interpolated Ab Initio Potentials." Annual Review of Physical Chemistry 72, no. 1 (April 20, 2021): 399–421. http://dx.doi.org/10.1146/annurev-physchem-090519-051837.

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The Born–Oppenheimer potential energy surface (PES) has come a long way since its introduction in the 1920s, both conceptually and in predictive power for practical applications. Nevertheless, nearly 100 years later—despite astonishing advances in computational power—the state-of-the-art first-principles prediction of observables related to spectroscopy and scattering dynamics is surprisingly limited. For example, the water dimer, (H2O)2, with only six nuclei and 20 electrons, still presents a formidable challenge for full-dimensional variational calculations of bound states and is considered out of reach for rigorous scattering calculations. The extremely poor scaling of the most rigorous quantum methods is fundamental; however, recent progress in development of approximate methodologies has opened the door to fairly routine high-quality predictions, unthinkable 20 years ago. In this review, in relation to the workflow of spectroscopy and/or scattering studies, we summarize progress and challenges in the component areas of electronic structure calculations, PES fitting, and quantum dynamical calculations.
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TO, TRAN THINH, and STEFAN ADAMS. "CHARGE TRANSPORT AND LIGHT ABSORPTION IN CONJUGATED SYSTEMS FROM EXTENDED HÜCKEL METHOD AND MARCUS THEORY." International Journal of Computational Materials Science and Engineering 01, no. 02 (June 2012): 1250020. http://dx.doi.org/10.1142/s2047684112500200.

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A simple first principle model was developed based on extended Hückel-type orbital calculation, Marcus electron transport theory and two-dimensional-electron-gas model for the treatment of charge transport in conjugated polymers. Though simple and easy to compute, the effect of the applied electric-field is factored in. Based on this, a complete one-dimensional device model with a single layer of conjugated polymer sandwiched between two electrodes was developed with poly(3-hexylthiophene) (P3HT) as a case study. Simulated J-V curves show that π-π charge transport is much more pronounced than intra-chain transport, hence agree with previous findings. Using the same framework, we also calculated the absorption spectra of P3HT by considering the electronic energy barrier for electronic transitions that would satisfy Franck–Condon principle. Absorption spectra closely harmonize to experimental UV-Vis result. The model also reveals intra-chain electronic transitions to be the dominant absorption mechanism. All parameters of the model are obtained from either ab-initio Density Functional Theory (DFT) or Molecular Dynamics (MD) calculations, so that this model is capable of predicting charge transport and light absorption properties of new conjugated polymers without introducing fit parameters.
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Segatta, Francesco, David M. Rogers, Naomi T. Dyer, Ellen E. Guest, Zhuo Li, Hainam Do, Artur Nenov, Marco Garavelli, and Jonathan D. Hirst. "Near-Ultraviolet Circular Dichroism and Two-Dimensional Spectroscopy of Polypeptides." Molecules 26, no. 2 (January 13, 2021): 396. http://dx.doi.org/10.3390/molecules26020396.

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A fully quantitative theory of the relationship between protein conformation and optical spectroscopy would facilitate deeper insights into biophysical and simulation studies of protein dynamics and folding. In contrast to intense bands in the far-ultraviolet, near-UV bands are much weaker and have been challenging to compute theoretically. We report some advances in the accuracy of calculations in the near-UV, which were realised through the consideration of the vibrational structure of the electronic transitions of aromatic side chains.
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Zhu, Zhengyang, Kai Ren, Huabing Shu, Zhen Cui, Zhaoming Huang, Jin Yu, and Yujing Xu. "First-Principles Study of Electronic and Optical Properties of Two-Dimensional WSSe/BSe van der Waals Heterostructure with High Solar-to-Hydrogen Efficiency." Catalysts 11, no. 8 (August 18, 2021): 991. http://dx.doi.org/10.3390/catal11080991.

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In this paper, the optical and electronic properties of WSSe/BSe heterostructure are investigated by first-principles calculations. The most stable stacking pattern of the WSSe/BSe compounds is formed by van der Waals interaction with a thermal stability proved by ab initio molecular dynamics simulation. The WSSe/BSe heterostructure exhibits a type-I band alignment with direct bandgap of 2.151 eV, which can improve the effective recombination of photoexcited holes and electrons. Furthermore, the band alignment of the WSSe/BSe heterostructure can straddle the water redox potential at pH 0–8, and it has a wide absorption range for visible light. In particular, the solar-to-hydrogen efficiency of the WSSe/BSe heterostructure is obtained at as high as 44.9% at pH 4 and 5. All these investigations show that the WSSe/BSe heterostructure has potential application in photocatalysts to decompose water.
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Autreto, P. A., J. M. de Sousa, and D. S. Galvao. "On the Dynamics of Graphdiyne Hydrogenation." MRS Proceedings 1549 (2013): 59–64. http://dx.doi.org/10.1557/opl.2013.608.

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ABSTRACTGraphene is a two-dimensional (2D) hexagonal array of carbon atoms in sp2-hybridized states. Graphene presents unique and exceptional electronic, thermal and mechanical properties. However, in its pristine state graphene is a gapless semiconductor, which poses some limitations to its use in some transistor electronics. Because of this there is a renewed interest in other possible two-dimensional carbon-based structures similar to graphene. Examples of this are graphynes and graphdiynes, which are two-dimensional structures, composed of carbon atoms in sp2 and sp-hybridized states. Graphdiynes (benzenoid rings connecting two acetylenic groups) were recently synthesized and they can be intrinsically nonzero gap systems. These systems can be easily hydrogenated and the amount of hydrogenation can be used to tune the band gap value. In this work we have investigated, through fully atomistic molecular dynamics simulations with reactive force field (ReaxFF), the structural and dynamics aspects of the hydrogenation mechanisms of graphdiyne membranes. Our results showed that depending on whether the atoms are in the benzenoid rings or as part of the acetylenic groups, the rates of hydrogenation are quite distinct and change in time in a very complex pattern. Initially, the most probable sites to be hydrogenated are the carbon atoms forming the triple bonds, as expected. But as the amount of hydrogenation increases in time this changes and then the carbon atoms forming single bonds become the preferential sites. The formation of correlated domains observed in hydrogenated graphene is no longer observed in the case of graphdiynes. We have also carried out ab initio DFT calculations for model structures in order to test the reliability of ReaxFF calculations.
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Pham, Thang, Sehoon Oh, Patrick Stetz, Seita Onishi, Christian Kisielowski, Marvin L. Cohen, and Alex Zettl. "Torsional instability in the single-chain limit of a transition metal trichalcogenide." Science 361, no. 6399 (July 19, 2018): 263–66. http://dx.doi.org/10.1126/science.aat4749.

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The scientific bounty resulting from the successful isolation of few to single layers of two-dimensional materials suggests that related new physics resides in the few- to single-chain limit of one-dimensional materials. We report the synthesis of the quasi–one-dimensional transition metal trichalcogenide NbSe3 (niobium triselenide) in the few-chain limit, including the realization of isolated single chains. The chains are encapsulated in protective boron nitride or carbon nanotube sheaths to prevent oxidation and to facilitate characterization. Transmission electron microscopy reveals static and dynamic structural torsional waves not found in bulk NbSe3 crystals. Electronic structure calculations indicate that charge transfer drives the torsional wave instability. Very little covalent bonding is found between the chains and the nanotube sheath, leading to relatively unhindered longitudinal and torsional dynamics for the encapsulated chains.
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Guskov, Vladislav, Fabian Langkabel, Matthias Berg, and Annika Bande. "An Impurity Effect for the Rates of the Interparticle Coulombic Decay." Quarks: Brazilian Electronic Journal of Physics, Chemistry and Materials Science 3, no. 1 (November 28, 2020): 17–30. http://dx.doi.org/10.34019/2674-9688.2020.v3.31928.

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The interparticle Coulombic decay is a synchronized decay and ionization phenomenon occurring on two separated and only Coulomb interaction coupled electron binding sites. This publication explores how drastically small environmental changes in between the two sites, basically impurities, can alter the ionization properties and process rate, although the involved electronic transitions remain unaltered. A comparison among the present electron dynamics calculations for the example of different types of quantum dots, accommodating a one- or a two-dimensional continuum for the outgoing electron, and the well-investigated atomic and molecular cases with three-dimensional continuum, reveals that the impurity effect is most pronounced the stronger that electron is confined. This necessarily leads to challenges and opportunities in a quantum dot experiment to prove the interparticle Coulombic decay.
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Cao, Bin, Ji-Wei Dong, and Ming-He Chi. "Electrical Breakdown Mechanism of Transformer Oil with Water Impurity: Molecular Dynamics Simulations and First-Principles Calculations." Crystals 11, no. 2 (January 27, 2021): 123. http://dx.doi.org/10.3390/cryst11020123.

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Water impurity is the essential factor of reducing the insulation performance of transformer oil, which directly determines the operating safety and life of a transformer. Molecular dynamics simulations and first-principles electronic-structure calculations are employed to study the diffusion behavior of water molecules and the electrical breakdown mechanism of transformer oil containing water impurities. The molecular dynamics of an oil-water micro-system model demonstrates that the increase of aging acid concentration will exponentially expedite thermal diffusion of water molecules. Density of states (DOS) for a local region model of transformer oil containing water molecules indicates that water molecules can introduce unoccupied localized electron-states with energy levels close to the conduction band minimum of transformer oil, which makes water molecules capable of capturing electrons and transforming them into water ions during thermal diffusion. Subsequently, under a high electric field, water ions collide and impact on oil molecules to break the molecular chain of transformer oil, engendering carbonized components that introduce a conduction electronic-band in the band-gap of oil molecules as a manifestation of forming a conductive region in transformer oil. The conduction channel composed of carbonized components will be eventually formed, connecting two electrodes, with the carbonized components developing rapidly under the impact of water ions, based on which a large number of electron carriers will be produced similar to “avalanche” discharge, leading to an electrical breakdown of transformer oil insulation. The water impurity in oil, as the key factor for forming the carbonized conducting channel, initiates the electric breakdown process of transformer oil, which is dominated by thermal diffusion of water molecules. The increase of aging acid concentration will significantly promote the thermal diffusion of water impurities and the formation of an initial conducting channel, accounting for the degradation in dielectric strength of insulating oil containing water impurities after long-term operation of the transformer.
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Katsavrias, C., I. A. Daglis, W. Li, S. Dimitrakoudis, M. Georgiou, D. L. Turner, and C. Papadimitriou. "Combined effects of concurrent Pc5 and chorus waves on relativistic electron dynamics." Annales Geophysicae 33, no. 9 (September 25, 2015): 1173–81. http://dx.doi.org/10.5194/angeo-33-1173-2015.

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Abstract. We present electron phase space density (PSD) calculations as well as concurrent Pc5 and chorus wave activity observations during two intense geomagnetic storms caused by interplanetary coronal mass ejections (ICMEs) resulting in contradicting net effect. We show that, during the 17 March 2013 storm, the coincident observation of chorus and relativistic electron enhancements suggests that the prolonged chorus wave activity seems to be responsible for the enhancement of the electron population in the outer radiation belt even in the presence of pronounced outward diffusion. On the other hand, the significant depletion of electrons, during the 12 September 2014 storm, coincides with long-lasting outward diffusion driven by the continuous enhanced Pc5 activity since chorus wave activity was limited both in space and time.
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Dissertations / Theses on the topic "ELECTRONS; TWO-DIMENSIONAL CALCULATIONS; DYNAMICS"

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Leonard, Darren J. T. "Dynamical properties of the two-dimensional electron gas." Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301235.

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Chowdhury, Sujaul Haque. "Transport of electrons in two-dimensional lateral surface superlattices." Thesis, University of Glasgow, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341952.

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Devitt, Andrew Maurice. "Time and angle resolved phonon absorption in the fractional quantum hall regime." Thesis, University of Nottingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342525.

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Storey, Marianne. "Effect of disorder on the melting phase transition." Thesis, Imperial College London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322000.

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Books on the topic "ELECTRONS; TWO-DIMENSIONAL CALCULATIONS; DYNAMICS"

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Raff, Lionel, Ranga Komanduri, Martin Hagan, and Satish Bukkapatnam. Neural Networks in Chemical Reaction Dynamics. Oxford University Press, 2012. http://dx.doi.org/10.1093/oso/9780199765652.001.0001.

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This monograph presents recent advances in neural network (NN) approaches and applications to chemical reaction dynamics. Topics covered include: (i) the development of ab initio potential-energy surfaces (PES) for complex multichannel systems using modified novelty sampling and feedforward NNs; (ii) methods for sampling the configuration space of critical importance, such as trajectory and novelty sampling methods and gradient fitting methods; (iii) parametrization of interatomic potential functions using a genetic algorithm accelerated with a NN; (iv) parametrization of analytic interatomic potential functions using NNs; (v) self-starting methods for obtaining analytic PES from ab inito electronic structure calculations using direct dynamics; (vi) development of a novel method, namely, combined function derivative approximation (CFDA) for simultaneous fitting of a PES and its corresponding force fields using feedforward neural networks; (vii) development of generalized PES using many-body expansions, NNs, and moiety energy approximations; (viii) NN methods for data analysis, reaction probabilities, and statistical error reduction in chemical reaction dynamics; (ix) accurate prediction of higher-level electronic structure energies (e.g. MP4 or higher) for large databases using NNs, lower-level (Hartree-Fock) energies, and small subsets of the higher-energy database; and finally (x) illustrative examples of NN applications to chemical reaction dynamics of increasing complexity starting from simple near equilibrium structures (vibrational state studies) to more complex non-adiabatic reactions. The monograph is prepared by an interdisciplinary group of researchers working as a team for nearly two decades at Oklahoma State University, Stillwater, OK with expertise in gas phase reaction dynamics; neural networks; various aspects of MD and Monte Carlo (MC) simulations of nanometric cutting, tribology, and material properties at nanoscale; scaling laws from atomistic to continuum; and neural networks applications to chemical reaction dynamics. It is anticipated that this emerging field of NN in chemical reaction dynamics will play an increasingly important role in MD, MC, and quantum mechanical studies in the years to come.
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Fox, Raymond. The Use of Self. Oxford University Press, 2011. http://dx.doi.org/10.1093/oso/9780190616144.001.0001.

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This monograph presents recent advances in neural network (NN) approaches and applications to chemical reaction dynamics. Topics covered include: (i) the development of ab initio potential-energy surfaces (PES) for complex multichannel systems using modified novelty sampling and feedforward NNs; (ii) methods for sampling the configuration space of critical importance, such as trajectory and novelty sampling methods and gradient fitting methods; (iii) parametrization of interatomic potential functions using a genetic algorithm accelerated with a NN; (iv) parametrization of analytic interatomic potential functions using NNs; (v) self-starting methods for obtaining analytic PES from ab inito electronic structure calculations using direct dynamics; (vi) development of a novel method, namely, combined function derivative approximation (CFDA) for simultaneous fitting of a PES and its corresponding force fields using feedforward neural networks; (vii) development of generalized PES using many-body expansions, NNs, and moiety energy approximations; (viii) NN methods for data analysis, reaction probabilities, and statistical error reduction in chemical reaction dynamics; (ix) accurate prediction of higher-level electronic structure energies (e.g. MP4 or higher) for large databases using NNs, lower-level (Hartree-Fock) energies, and small subsets of the higher-energy database; and finally (x) illustrative examples of NN applications to chemical reaction dynamics of increasing complexity starting from simple near equilibrium structures (vibrational state studies) to more complex non-adiabatic reactions. The monograph is prepared by an interdisciplinary group of researchers working as a team for nearly two decades at Oklahoma State University, Stillwater, OK with expertise in gas phase reaction dynamics; neural networks; various aspects of MD and Monte Carlo (MC) simulations of nanometric cutting, tribology, and material properties at nanoscale; scaling laws from atomistic to continuum; and neural networks applications to chemical reaction dynamics. It is anticipated that this emerging field of NN in chemical reaction dynamics will play an increasingly important role in MD, MC, and quantum mechanical studies in the years to come.
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Glazov, M. M. Electron & Nuclear Spin Dynamics in Semiconductor Nanostructures. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198807308.001.0001.

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In recent years, the physics community has experienced a revival of interest in spin effects in solid state systems. On one hand, solid state systems, particularly semicon- ductors and semiconductor nanosystems, allow one to perform benchtop studies of quantum and relativistic phenomena. On the other hand, interest is supported by the prospects of realizing spin-based electronics where the electron or nuclear spins can play a role of quantum or classical information carriers. This book aims at rather detailed presentation of multifaceted physics of interacting electron and nuclear spins in semiconductors and, particularly, in semiconductor-based low-dimensional structures. The hyperfine interaction of the charge carrier and nuclear spins increases in nanosystems compared with bulk materials due to localization of electrons and holes and results in the spin exchange between these two systems. It gives rise to beautiful and complex physics occurring in the manybody and nonlinear system of electrons and nuclei in semiconductor nanosystems. As a result, an understanding of the intertwined spin systems of electrons and nuclei is crucial for in-depth studying and control of spin phenomena in semiconductors. The book addresses a number of the most prominent effects taking place in semiconductor nanosystems including hyperfine interaction, nuclear magnetic resonance, dynamical nuclear polarization, spin-Faraday and -Kerr effects, processes of electron spin decoherence and relaxation, effects of electron spin precession mode-locking and frequency focusing, as well as fluctuations of electron and nuclear spins.
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Book chapters on the topic "ELECTRONS; TWO-DIMENSIONAL CALCULATIONS; DYNAMICS"

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Kuramoto, Y. "Exact Dynamics of Highly Correlated Electrons in Two Dimensions." In New Horizons in Low-Dimensional Electron Systems, 247–60. Dordrecht: Springer Netherlands, 1992. http://dx.doi.org/10.1007/978-94-011-3190-2_17.

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Jacoboni, Carlo, Paolo Casarini, and Alice Ruini. "Two-Dimensional Dynamics of Electrons Passing Through a Point Contact." In Quantum Transport in Ultrasmall Devices, 181–90. Boston, MA: Springer US, 1995. http://dx.doi.org/10.1007/978-1-4615-1967-6_8.

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Evertz, H. G., and D. P. Landau. "Spin Dynamics Calculations in the Two-Dimensional Classical XY-Model." In Springer Proceedings in Physics, 175–79. Berlin, Heidelberg: Springer Berlin Heidelberg, 1995. http://dx.doi.org/10.1007/978-3-642-79991-4_22.

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Raff, Lionel, Ranga Komanduri, Martin Hagan, and Satish Bukkapatnam. "Summary, Conclusions, and Future Trends." In Neural Networks in Chemical Reaction Dynamics. Oxford University Press, 2012. http://dx.doi.org/10.1093/oso/9780199765652.003.0015.

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Since the introduction of classical and semiclassical molecular dynamics (MD) methods in the 1960s and Gaussian procedures to conduct electronic structure calculations in the 1970s, a principal objective of theoretical chemistry has been to combine the two methods so that MD and quantum mechanical studies can be conducted on ab initio potential surfaces. Although numerous procedures have been attempted, the goal of first principles, ab initio dynamics calculations has proven to be elusive when the system contains five or more atoms moving in unrestricted three-dimensional space. For many years, the conventional wisdom has been that ab initio MD calculations for complex systems containing five or more atoms with several open reaction channels are presently beyond our computational capabilities. The rationale for this view are (a) the inherent difficulty of high level ab initio quantum calculations on complex systems that may take numerous, large-scale computations impossible, (b) the large dimensionality of the configuration space for such systems that makes it necessary to examine prohibitively large numbers of nuclear configurations, and (c) the extreme difficulty associated with obtaining sufficiently converged results to permit accurate interpolation of numerical data obtained from electronic structure calculations when the dimensionality of the system is nine or greater. Neural networks (NN) derive their name from the fact that their interlocking structure superficially resembles the neural network of a human brain and from the fact that NNs can sense the underlying correlations that exist in a database and properly map them in a manner analogous to the way a human brain can execute pattern recognition. Artificial neurons were first proposed in 1943 by Warren McCulloch, a neurophysiologist, and Walter Pitts, an MIT logician. NNs have been employed by engineers for decades to assist in the solution of a multitude of problems. Nevertheless, the power of NNs to assist in the solution of numerous problems that occur in chemical reaction dynamics is just now being realized by the chemistry community.
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Tsui, D. C. "Correlation and localization of two-dimensional electrons in a strong magnetic field." In Lattice Dynamics and Semiconductor Physics, 460–77. WORLD SCIENTIFIC, 1989. http://dx.doi.org/10.1142/9789814368346_0021.

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Schäfer, Lothar, and John D. Ewbank. "On Comparing Experimental and Calculated Structural Parameters." In Molecular Orbital Calculations for Biological Systems. Oxford University Press, 1998. http://dx.doi.org/10.1093/oso/9780195098730.003.0010.

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The tacit assumption underlying all science is that, of two competing theories, the one in closer agreement with experiment is the better one. In structural chemistry the same principle applies but, when calculated and experimental structures are compared, closer is not necessarily better. Structures from ab initio calculations, specifically, must not be the same as the experimental counterparts the way they are observed. This is so because ab initio geometries refer to nonexistent, vibrationless states at the minimum of potential energy, whereas structural observables represent specifically defined averages over distributions of vibrational states. In general, if one wants to make meaningful comparisons between calculated and experimental molecular structures, one must take recourse of statistical formalisms to describe the effects of vibration on the observed parameters. Among the parameters of interest to structural chemists, internuclear distances are especially important because other variables, such as bond angles, dihedral angles, and even crystal spacings, can be readily derived from them. However, how a rigid torsional angle derived from an ab initio calculation compares with the corresponding experimental value in a molecule subject to vibrational anharmonicity, is not so easy to determine. The same holds for the lattice parameters of a molecule in a dynamical crystal, and their temperature dependence as a function of the molecular potential energy surface. In contrast, vibrational effects are readily defined and best described for internuclear distances, bonded and non-bonded ones. In general, all observed internuclear distances are vibrationally averaged parameters. Due to anharmonicity, the average values will change from one vibrational state to the next and, in a molecular ensemble distributed over several states, they are temperature dependent. All these aspects dictate the need to make statistical definitions of various conceivable, different averages, or structure types. In addition, since the two main tools for quantitative structure determination in the vapor phase—gas electron diffraction and microwave spectroscopy—interact with molecular ensembles in different ways, certain operational definitions are also needed for a precise understanding of experimental structures. To illustrate how the operations of an experimental technique affect the nature of its observables, gas electron diffraction shall be used as an example.
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Raff, Lionel, Ranga Komanduri, Martin Hagan, and Satish Bukkapatnam. "Overview of Some Non –Neural Network Methods for Fitting Ab Initio Potential-Energy Databases." In Neural Networks in Chemical Reaction Dynamics. Oxford University Press, 2012. http://dx.doi.org/10.1093/oso/9780199765652.003.0006.

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In this chapter, we describe results obtained by five methods that have been employed to fit ab initio potential-energy. These methods are (i) moving or modified Shepard interpolation (MSI), (ii) interpolative moving least squares (IMLS), (iii) invariant polynomials (IP), (iv) reproducing kernel Hilbert space (RKHS), and (v) a hybrid method that combines MSI and IMLS methods. The MSI and IMLS methods are described in some detail in the following. The IP and RKHS procedures are significantly more complex, and the reader is referred to the original papers for a more complete discussion of the details by which these methods are executed. The moving or modified Shepard interpolation (MSI) method was developed primarily by Collins and co-workers. The method employs electronic structure calculations to obtain the molecular potential energy at configuration points generated by an automated procedure. These data are then employed in a Shepard interpolation procedure to obtain the potential energies of the system at points other than those in the database. This procedure involves expressing the local potential about each configuration point in a Taylor series expansion. The term “moving” in the title derives from the fact that the set of internal coordinates employed in the interpolation varies from point-to-point in the database. Like all fitting methods, the MSI procedure requires the potential energy at a set of configuration points in the (3N-6) dimensional internal space of the system under investigation. These energies are generally obtained using ab initio electronic structure methods at some level of accuracy. In addition to the potential energies at each configuration point, the method also requires at least the first and second derivatives of the potential with respect to the coordinates being employed at each configuration point. These derivatives are needed to allow the local potential about a given configuration point in the database to be expressed in terms of a Taylor series expansion about that point. In principle, the MSI method may be extended to include third or fourth derivatives, but in most applications, the expansions are truncated after the quadratic terms.
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Warrick, Arthur W. "Saturated Flow." In Soil Water Dynamics. Oxford University Press, 2003. http://dx.doi.org/10.1093/oso/9780195126051.003.0008.

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Saturated conditions generally exist below a water table, either as part of the permanent groundwater system (aquifer) or in the vadose zone as perched water. For isotropic and steady-state conditions, such systems can be modeled by Laplace’s equation. Because it is linear, Laplace’s equation is much easier to solve than the variably saturated forms of Richards’ equation and, hence, provides a convenient place to begin. Analyses of water flow for drainage and groundwater systems borrow heavily from the classical (and old!) work in heat conduction, hydrodynamics, and electrostatics. This section presents analytical solutions for subsurface drainage and well discharge in fully penetrating confined aquifers (the solutions are the same). Included are the definition of stream functions and demonstrations of the Cauchy–Riemann relations. A comparable numerical solution is presented, and also for the ponded drainage and well discharge, and the results compared with the analytical solutions. A more complex example is then presented concerning drainage below a curved water table. These results are followed by travel-time calculations relevant to solute movement from the soil surface to a drainage system. A short section covering analytical techniques with three-dimensional images is then given, followed by a section covering additional topics, which includes a complex image example (two dimensional) and some relationships for Fourier series. Consider a point source in a two-dimensional x—y plane, as in figure 3-1. The origin corresponds to a source that is assumed to be an infinite line perpendicular to the x—y plane. If the steady flow rate is Q, then the conservation of mass results in . . . Q = Jr(2πr) (3-1) . . . where Jr is the Darcian flow in the r direction and evaluated at a polar radius r. The dimensions of Q are [L2T-1] corresponding to a volume of flow per unit time from a unit length of the line perpendicular to the x—y plane. Values of Q are taken to be positive for water entering the system.
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Dyall, Kenneth G., and Knut Faegri. "Correlation Methods." In Introduction to Relativistic Quantum Chemistry. Oxford University Press, 2007. http://dx.doi.org/10.1093/oso/9780195140866.003.0018.

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It is well known from nonrelativistic quantum chemistry that mean-field methods, such as the Hartree–Fock (HF) model, provide mainly qualitative insights into the electronic structure and bonding of molecules. To obtain reliable results of “chemical accuracy” usually requires models that go beyond the mean field and account for electron correlation. There is no reason to expect that the mean-field approach should perform significantly better in this respect for the relativistic case, and so we are led to develop schemes for introducing correlation into our models for relativistic quantum chemistry. There is no fundamental change in the concept of correlation between relativistic and nonrelativistic quantum chemistry: in both cases, correlation describes the difference between a mean-field description, which forms the reference state for the correlation method, and the exact description. We can also define dynamical and nondynamical correlation in both cases. There is in fact no formal difference between a nonrelativistic spin–orbital-based formalism and a relativistic spinor-based formalism. Thus we should be able to transfer most of the schemes for post-Hartree–Fock calculations to a relativistic post-Dirac–Hartree–Fock model. Several such schemes have been implemented and applied in a range of calculations. The main technical differences to consider are those arising from having to deal with integrals that are complex, and the need to replace algorithms that exploit the nonrelativistic spin symmetry by schemes that use time-reversal and double-group symmetry. In addition to these technical differences, however, there are differences of content between relativistic and nonrelativistic methods. The division between dynamical and nondynamical correlation is complicated by the presence of the spin–orbit interaction, which creates near-degeneracies that are not present in the nonrelativistic theory. The existence of the negative-energy states of relativistic theory raise the question of whether they should be included in the correlation treatment. The first two sections of this chapter are devoted to a discussion of these issues. The main challenges in the rest of this chapter are to handle the presence of complex integrals and to exploit time-reversal symmetry.
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Baer, Tomas, and William L. Hase. "Dynamical Approaches to Unimolecular Rates." In Unimolecular Reaction Dynamics. Oxford University Press, 1996. http://dx.doi.org/10.1093/oso/9780195074949.003.0010.

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In the previous chapters theories were discussed for calculating the unimolecular rate constant as a function of energy and angular momentum. The assumption inherent in these theories is that a microcanonical ensemble is maintained during the unimolecular reaction and that every state in the energy interval E → E + dE has an equal probability of decomposing. Such theories are viewed as statistical since the unimolecular rate constant is found from a statistical counting of states in the microcanonical ensemble. A dynamical description of unimolecular decomposition is concerned with properties of individual states of the energized molecule. Of interest are the decomposition probabilities for the states as well as the rate of transitions between the states. Dynamical theories of unimolecular decomposition deal with the properties of vibrational/rotational energy levels, state preparation and intramolecular vibrational energy redistribution (IVR). Thus, the presentation in this chapter draws extensively on the previous chapters 2 and 4. Unimolecular decomposition dynamics can be treated using quantum and classical mechanics, and both perspectives are considered here. The role of nonadiabatic electronic transitions in unimolecular dynamics is also discussed. A molecule which can dissociate does not, strictly speaking, have a discrete energy spectrum. The relative motion of the product fragments is unbounded and, in this sense the motion of the unimolecular system is infinite, and hence the energy spectrum is continuous. However, it may happen that the dissociation probability of the molecule is sufficiently small that one can introduce the concept of quasi-stationary states. Such states are commonly referred to as resonances since the energy of the unimolecular fragments in the continuum is in resonance with (i.e., matches) the energy of a vibrational/rotational level of the unimolecular reactant. For unimolecular reactions there are two types of resonance states. The simplest type, a shape resonance, occurs when a molecule is temporarily trapped by a fairly high and wide potential energy barrier. The second type of resonance, called a Feshbach or compound-state resonance, occurs when energy is initially distributed between vibrational/rotational degrees of freedom of the molecule which are not strongly coupled to the fragment relative motion, so that there is a time lag for unimolecular dissociation.
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Conference papers on the topic "ELECTRONS; TWO-DIMENSIONAL CALCULATIONS; DYNAMICS"

1

Cassiano, Tiago de Sousa Araújo, Fábio Ferreira Monteiro, and Pedro Henrique de Oliveira Neto. "Unveiling the Dynamics of Quasiparticles in Cove-type Graphene Nanoribbons." In VIII Simpósio de Estrutura Eletrônica e Dinâmica Molecular. Universidade de Brasília, 2020. http://dx.doi.org/10.21826/viiiseedmol202074.

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Since its isolation in 2004, graphene has attracted the attention of many scientists due to its excellent transport and mechanical features. However, the use of this material in optoelectronics is limited since it has no bandgap. One can detour it by cutting a graphene sheet laterally. The new carbon nanostructure that emerges from this procedure is known as graphene nanoribbon (GNR). Nowadays, a quest to develop a viable production of these materials drives many researchers. Narita et al.[2] successfully synthesized a candidate using a bottom-up solution procedure, known as cove-type GNR. Despite all the promising attributes, the electronic transport mechanism of this material is so far unexplored. In this work, we investigated through computational simulations the electronic transport of the cove-type GNR. We did so by employing an extended two-dimensional SSH model [3] with a tight-binding effect (electron-phonon coupling). A self-consistent field method generates stationary states, while time evolution is conducted based on the Ehrenfest theorem. Results reveal the formation of two polarized regions after photoionization: a polaron and a bipolaron. These quasiparticles are mobile by the application of a uniform electric field, unveiling its role as a charge transporter. Finally, a semi-classical algorithm evaluates their mobility and effective mass. Calculations indicate that both structures have a low effective mass along with intrinsic mobility. Hence, the cove-type GNRs may be suitable to perform as highly efficient semiconductors in future applications. This study contributes as well to the theoretical understanding of confined quantum systems.
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KHOSLA, P., T. LIANG, S. RUBIN, and M. HAGENMAIER. "Supersonic viscous flow calculations for axisymmetric, two and three-dimensional configurations." In 22nd Fluid Dynamics, Plasma Dynamics and Lasers Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1991. http://dx.doi.org/10.2514/6.1991-1802.

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3

GLAZ, HARLAND, PHILLIP COLELLA, JAMES COLLINS, and RALPH FERGUSON. "High resolution calculations of unsteady, two-dimensional nonequilibrium gas dynamics with experimental comparisons." In 19th AIAA, Fluid Dynamics, Plasma Dynamics, and Lasers Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1987. http://dx.doi.org/10.2514/6.1987-1293.

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4

MONSON, D., H. SEEGMILLER, and P. MCCONNAUGHEY. "Comparison of experiment with calculations using curvature-correctedzero and two equation turbulence models for a two-dimensional U-duct." In 21st Fluid Dynamics, Plasma Dynamics and Lasers Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1990. http://dx.doi.org/10.2514/6.1990-1484.

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5

BATINA, J. "Unsteady transonic flow calculations for two-dimensional canard-wingconfigurations with aeroelastic applications." In 26th Structures, Structural Dynamics, and Materials Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1985. http://dx.doi.org/10.2514/6.1985-585.

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6

Lin, P., L. Martinelli, T. Baker, and A. Jameson. "Two-dimensional implicit time dependent calculations for incompressible flows on adaptive unstructured meshes." In 15th AIAA Computational Fluid Dynamics Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2001. http://dx.doi.org/10.2514/6.2001-2655.

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7

Ji, Pengfei, Mengzhe He, Yiming Rong, Yuwen Zhang, and Yong Tang. "Multiscale Investigation of Thickness Dependent Melting Thresholds of Nickel Film Under Femtosecond Laser Heating." In ASME 2018 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/imece2018-86947.

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A multiscale modeling that integrates electronic scale ab initio quantum mechanical calculation, atomic scale molecular dynamics simulation, and continuum scale two-temperature model description of the femtosecond laser processing of nickel film at different thicknesses is carried out in this paper. The electron thermophysical parameters (heat capacity, thermal conductivity, and electron-phonon coupling factor) are calculated from first principles modeling, which are further substituted into molecular dynamics and two-temperature model coupled energy equations of electrons and phonons. The melting thresholds for nickel films of different thicknesses are determined from multiscale simulation. Excellent agreement between results from simulation and experiment is achieved, which demonstrates the validity of modeled multiscale framework and its promising potential to predict more complicate cases of femtosecond laser material processing. When it comes to process nickel film via femtosecond laser, the quantitatively calculated maximum thermal diffusion length provides helpful information on choosing the film thickness.
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Sumali, Hartono, Jeffrey W. Martin, Pavel Chaplya, and James M. Redmond. "Shape Control of a Flexible Mirror Using an Electron Gun." In ASME 2003 International Mechanical Engineering Congress and Exposition. ASMEDC, 2003. http://dx.doi.org/10.1115/imece2003-41084.

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Mirrors made of PVDF film are being considered for lightweight transportation and deployment in space. An array of electrodes can be used to distribute charges over the PVDF film for active shaping of the mirrors. This paper presents the derivation of a matrix that enables calculation of the shape of the two-dimensional mirror for any given electron distribution. Finite element simulation shows good agreement with a theoretical example. Furthermore, if a desired shape is given, the required voltage distribution can be computed using the singular value decomposition. Experiments were done in a vacuum vessel, where an electron gun was used to actuate a PVDF bimorph to a desired shape. Dynamic shape control is attainable at low frequencies. At higher frequencies, still significantly below structural resonance, actuation lag and parasitic DC offset can be significant problems that require future research to solve.
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Xia, J. L., T. Ahokainen, and T. Kankaanpa¨a¨. "Effect of Electrode Shape and Heat Loss Rates on Slag Flow and Heat Transfer." In ASME 2003 International Mechanical Engineering Congress and Exposition. ASMEDC, 2003. http://dx.doi.org/10.1115/imece2003-43523.

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Cylindrical electrode geometry was used in past studies, while practically the electrode is of conical shape. the present paper numerically simulates three-dimensional magnetohydro-dynamic flow in an electric furnace with three electrodes immersed into the slag by using an idealized cylindrical and an actual conical electrode shape. Calculations are also carried out for different heat loss rates along the free surface and teh furnace wall. Results show that the electrode shape has slight influence on slag flow behavior and the cylindrical electrode geometry may be used in case without information of actual electrode shape. It is important to correctly specify the boundary conditions at the free surface and the furnace wall in order to obtain reasonable prediction for the slag flow and heat transfer, and reasonable ranges of these conditions are obtained for the furnace considered.
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Márk, Géza I. "Full three-dimensional wave-packet dynamical calculations of STM images of nanotube Y-junctions." In STRUCTURAL AND ELECTRONIC PROPERTIES OF MOLECULAR NANOSTRUCTURES: XVI International Winterschool on Electronic Properties of Novel Materials. AIP, 2002. http://dx.doi.org/10.1063/1.1514145.

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