A Density-Genetic Algorithm Method for Computing Electronic Structures of Doped and Undoped Polythiophene Oligomers: A Modified Su-Schrieffer-Heeger Hamiltonian-Based Study
08 Apr 2011-Materials and Manufacturing Processes (Taylor & Francis Group)-Vol. 26, Iss: 3, pp 354-362
TL;DR: In this article, a GA-driven density matrix method for calculating the equilibrium geometry and charge storage configurations of hole-bipolaron-doped polythiophene (PT) oligomers is proposed.
Abstract: We propose a genetic algorithm (GA)-driven density matrix method for calculating the equilibrium geometry and charge storage configurations of hole(bipolaron)-doped Polythiophene (PT) oligomers. A modified version of the Su–Schrieffer–Heeger Hamiltonian is used to describe the PT chain. A population of geometry strings are used to generate the corresponding PT-Hamiltonians which act as generators of corresponding unitary transformations which transform a single trial one-electron density matrix into a population of density matrices for different geometries. As the geometry strings evolve under the action of GA operators, the density matrices also evolve on the fitness landscape. Once the fitness reaches maximum, the optimum geometry string, the corresponding Hamiltonian, and the density matrix lead to equilibrium geometry, energy, charge distribution, band gap, Fermi energy, etc. The bipolaronic defect–induced conducting state is predicted to have a symmetric lattice-like admixture of “aromatic” and “quin...
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TL;DR: The representative examples selected from recent literature show how broad is the usefulness of this computational method in materials science and related fields.
Abstract: Genetic algorithms (GAs) are a tool used to solve high-complexity computational problems. Apart from modelling the phenomena occurring in Nature, they help in optimization, simulation, modelling, design and prediction purposes in science, medicine, technology, and everyday life. They can be adapted to the given task, be joined with other ones (this leads to combined or hybrid methods), and can work in parallel on many processors. The uses of GAs reported in literature represent a wide variety of approaches and led to solving of numerous computational problems of high complexity. In materials science and related fields of science and technology the GAs open possibilities for materials design, studies of their properties, or production at industrial scale. Here, the recent use of GAs in various domains connected to materials science, solid state physics and chemistry, crystallography, biology, and engineering is reviewed. The listed examples taken from recent literature show how broad the use of these metho...
146 citations
TL;DR: In this paper, the authors studied the shear deformation analysis and diffusion behavior of copper-Zirconium Bulk Metallic Glasses (BMG) for different combinations of processing parameters.
Abstract: Shear deformation analysis and diffusion behavior of Copper-Zirconium Bulk Metallic Glasses (BMG) is studied for different combinations of processing parameters. Melt holding temperature, melt holding duration, cooling rate of melt and composition of BMG are varied to obtain BMGs of different structures. The as-quenched structures are characterized using Radial Distribution Function (RDF) and Self-Diffusion constant values (of each atom type). The objective of this study is to design a Cu-Zr BMG which can absorb maximum energy and still deform as little as possible while maximizing its diffusivity during shear deformation of the structure. For this, metamodels were constructed by feeding the Molecular Dynamics (MD) results to an Evolutionary Neural Network (EvoNN) so as to generate the desired objective functions which are then optimized through multiobjective genetic algorithm. This led to identification of some hitherto unknown structures, characterized by atomic coordinates, which have good resistance ...
15 citations
Cites background from "A Density-Genetic Algorithm Method ..."
...Although the science of characterizing glassy structures in terms of atomic arrangement is still at an emerging stage, the structures with a predetermined combination of properties can now be generated at the atomic scale by mapping the simulation parameters onto the atomic structure, using an evolutionary approach, as has been done successfully for the crystalline materials [23, 24]....
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TL;DR: In this paper, the shearing process of polycrystalline Zn coated Fe is simulated in the presence of dislocations, using molecular dynamics and fed to an Evolutionary Neural Network generated the meta-models of objective functions required in the subsequent Paretooptimization task using a multi-objective genetic algorithm.
Abstract: To design a coating that will absorb maximum energy prior to failure with minimum deformation, the shearing process of polycrystalline Zn coated Fe is simulated in the presence of dislocations, using molecular dynamics The results fed to an Evolutionary Neural Network generated the meta-models of objective functions required in the subsequent Pareto-optimization task using a Multi-objective Genetic Algorithm Similar calculations conducted for single crystals, and also in the absence of dislocations, are compared and analyzed
10 citations
TL;DR: In this article, a suitable Stillinger-Weber (SW) potential energy function parameter set for finite boron structures by genetic algorithm and trial error techniques is developed, where Boron structure geometries in 7-24 atoms range, calculated by ab initio methods, are taken as the fitting criteria in the parameter set development.
Abstract: A suitable Stillinger–Weber (SW) potential energy function parameter set is developed for finite boron structures by genetic algorithm and trial error techniques. Boron structure geometries in 7–24 atoms range, calculated by ab initio methods, are taken as the fitting criteria in the parameter set development. This parameter set is used together with another SW parameter set developed for carbon–carbon interactions in order to investigate boron carbide nanoparticles in the form of B x C x where 8 ⩽ x ⩽ 14. In addition, B 80 C 12 nanoparticle structure is investigated using local optimization technique.
7 citations
References
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Book•
01 Jan 1975
TL;DR: Names of founding work in the area of Adaptation and modiication, which aims to mimic biological optimization, and some (Non-GA) branches of AI.
Abstract: Name of founding work in the area. Adaptation is key to survival and evolution. Evolution implicitly optimizes organisims. AI wants to mimic biological optimization { Survival of the ttest { Exploration and exploitation { Niche nding { Robust across changing environments (Mammals v. Dinos) { Self-regulation,-repair and-reproduction 2 Artiicial Inteligence Some deenitions { "Making computers do what they do in the movies" { "Making computers do what humans (currently) do best" { "Giving computers common sense; letting them make simple deci-sions" (do as I want, not what I say) { "Anything too new to be pidgeonholed" Adaptation and modiication is root of intelligence Some (Non-GA) branches of AI: { Expert Systems (Rule based deduction)
32,573 citations
"A Density-Genetic Algorithm Method ..." refers background or methods in this paper
...in defect states can be viewed as a complex optimization problem and the power of genetic algorithms [12] invoked to handle the task....
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...We may avoid the gradient calculations and still ensure globality of the search by adopting a GA-based search for the optimum geometry [12, 18]....
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TL;DR: In this paper, the authors present a theoretical study of soliton formation in long-chain polyenes, including the energy of formation, length, mass, and activation energy for motion.
Abstract: We present a theoretical study of soliton formation in long-chain polyenes, including the energy of formation, length, mass, and activation energy for motion. The results provide an explanation of the mobile neutral defect observed in undoped ${(\mathrm{CH})}_{x}$. Since the soliton formation energy is less than that needed to create band excitation, solitons play a fundamental role in the charge-transfer doping mechanism.
4,562 citations
TL;DR: A theoretical analysis of the excitation spectrum of long-chain polyenes is presented in this paper, where one electronic state is localized at the gap center for each soliton or antisoliton present and the soliton's energy of formation, length, mass, activation energy for motion, and electronic properties are calculated.
Abstract: A theoretical analysis of the excitation spectrum of long-chain polyenes is presented. Because of the twofold degeneracy of the ground state of the dimerized chain, elementary excitations corresponding to topological solitons are obtained. The solitons can have three charge states $Q=0$. $\ifmmode\pm\else\textpm\fi{}e$. The neutral soliton has spin one-half while the charged solitons have spin zero. One electronic state is localized at the gap center for each soliton or antisoliton present. The soliton's energy of formation, length, mass, activation energy for motion, and electronic properties are calculated. These results are compared with experiment.
2,276 citations
TL;DR: This work presents a method for reliably determining the lowest energy structure of an atomic cluster in an arbitrary model potential, based on a genetic algorithm that operates on a population of candidate structures to produce new candidates with lower energies.
Abstract: We present a method for reliably determining the lowest energy structure of an atomic cluster in an arbitrary model potential. The method is based on a genetic algorithm, which operates on a population of candidate structures to produce new candidates with lower energies. Our method dramatically outperforms simulated annealing, which we demonstrate by applying the genetic algorithm to a tight-binding model potential for carbon. With this potential, the algorithm efficiently finds fullerene cluster structures up to ${\mathrm{C}}_{60}$ starting from random atomic coordinates.
1,002 citations
"A Density-Genetic Algorithm Method ..." refers background in this paper
...There is a rich body of literature [13–19] starting with the seminal work of Deaven and Ho [13], illustrating the versatility of GAs in searching through the complex potential energy landscapes of atomic clusters....
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TL;DR: The role of excitonic coupling on the nature of photoexcitations in the conjugated polymer regioregular poly(3-hexylthiophene) is addressed by means of temperature-dependent absorption and photoluminescence spectroscopy.
Abstract: We address the role of excitonic coupling on the nature of photoexcitations in the conjugated polymer regioregular poly(3-hexylthiophene). By means of temperature-dependent absorption and photoluminescence spectroscopy, we show that optical emission is overwhelmingly dominated by weakly coupled H aggregates. The relative absorbance of the 0-0 and 0-1 vibronic peaks provides a powerfully simple means to extract the magnitude of the intermolecular coupling energy, of approximately 5 and 30 meV for films spun from isodurene and chloroform solutions, respectively.
848 citations