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Topic: Electronic structure

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Molecular orbital

Shell model

Linus Pauling

	Electronic band structure - Wikipedia, the free encyclopedia
		The nearly-free electron approximation in solid state physics is similar in some respects to the Hydrogen-like atom of quantum mechanics in that interactions between electrons are completely ignored.
		Although the nearly-free electron approximation is able to describe many properties of electron band structures, one consequence of this theory is that it predicts the same number of electrons in each unit cell.
		The band structure has been generalised to wavevectors that are complex numbers, resulting in what is called a complex band structure, which is of interest at surfaces and interfaces.
	en.wikipedia.org /wiki/Electronic_band_structure (1103 words)

	Electronic band structure -- Facts, Info, and Encyclopedia article (Site not responding. Last check: 2007-10-07)
		Although electronic band structures are usually associated with crystalline materials, quasi-crystalline and amorphous materials may also exhibit band structures.
		Although there may be an infinite number of bands in the band structure of a given material, there are two bands that are of particular significance in determining the electronic and optical properties of a material.
		Because electron momentum is the recipricol of space, the dispersion relation between the energy and momentum of electrons can best be described in reciprocal space.
	www.absoluteastronomy.com /encyclopedia/e/el/electronic_band_structure.htm (793 words)

	Charles Bury on Electronic Structure in 1921
		For the structure of the elements of this period, Langmuir doubles the electrons in the cells of the second layer.
		Electrons meet with little resistance in passing into the inner layer: the elements have no tendency to form compounds in which they exhibit a high valence, and their divalent salts are found to be the most stable.
		Tantalum and tungsten have the structures (2,8,18,32,8,5) and (2,8,18,32,8,6,), and are analogous to columbium and molybdenum.
	dbhs.wvusd.k12.ca.us /webdocs/Chem-History/Bury-1921.html (3052 words)

	CHEMystery: Atomic Structure and Bonding: Variation of Atomic Properties with Electronic Structure (Site not responding. Last check: 2007-10-07)
		When electrons are removed from an atom (creating a positive ion), the repulsions decrease, and the remaining electrons are drawn closer to the nucleus, therefore making the size of the ion smaller than the neutral atom.
		Electron affinity (EA) is the potential energy change associated with the addition of an electron to a gaseous atom or ion in its ground state.
		For nearly all elements, the addition of one electron to a neutral atom is exothermic, and the EA is a negative value.
	library.thinkquest.org /3659/structures/variation.html (568 words)

	NREL-SST: Reverse Enineer Atomic Electronic Structures
		The distance between the electronic structure of the configuration and what is wanted is determined and minimized by varying the configuration variables, using electronic structure theory.
		Since they are interested in electronic properties that involve band-edge energy level and wave function, the Hamiltonian is diagonalized using a computationally efficient method that focuses on an energy window around the bandgap.
		They applied their method to semiconductor alloys and superlattices, but the algorithm could be applied to the optimization of the electronic structure of complex molecules and clusters as well.
	www.sst.nrel.gov /media_cov/reverseNT.html (637 words)

	An Introduction to the Electronic Structure of Atoms in Molecules
		An Introduction to the Electronic Structure of Atoms and Molecules
		Thus, given the molecular charge distribution, the stability of a chemical bond may be discussed in terms of the electrostatic requirement of achieving a zero force on the nuclei in the molecule.
		The alternative interpretation of the probability distribution (for a stationary state of an atom) as a representation of a static distribution of electronic charge in real space is stressed, in preparation for the discussion of the chemical bond.
	www.chemistry.mcmaster.ca /esam (764 words)

	Molecular Orbitals - Molecular Orbitals for Homonuclear Diatomics
		8-4) is as fundamental to the understanding of the electronic structure of diatomic molecules as the corresponding atomic orbital diagram is to the understanding of atoms.
		We are now in a position to build up and determine the electronic configurations of the homonuclear diatomic molecules by adding electrons two at a time to the molecular orbitals with the spins of the electrons paired, always filling the orbitals of lowest energy first.
		Excited electronic configurations for molecules may be described and predicted with the same ease within the framework of molecular orbital theory as are the excited configurations of atoms in the corresponding atomic orbital theory.
	www.chemistry.mcmaster.ca /esam/Chapter_8/section_3.html (2734 words)

	Electron configuration
		In chemistry, the term "electron configuration" refers to the arrangement of electrons; as they "orbit" around the nuclei of one, or more, atoms.
		The first quantum number n corresponds to the overall energy and hence also the distance from the nucleus of an orbital, hence sets of states with the same n are often referred to as electron shells or energy levels.
		These are not sharply delineated zones within the atom, but rather fuzzy-edged regions within which an electron is likely to be found, due to the probabilistic nature of quantum mechanical wavefunctions.
	www.brainyencyclopedia.com /encyclopedia/e/el/electron_configuration.html (925 words)

	Institutional Research Plan A - 8. Structure and Electronic States of Solids
		The determination of the structure is the unifying idea of the research which, from a methodological point of view, can be split into three research activities: analysis of x-ray diffraction data, analysis of spectroscopic data and total-energy quantum mechanical calculations based on first principle methods.
		X-ray diffraction: The structure analysis will be based on our original software JANA which is currently one of the leading systems in the field of the structure analysis of aperiodic and complicated periodic crystals.
		The ambition of all these projects is to develop a general system working for three-dimensional as well as multidimensional structures, single domain, multidomain or intergrowth crystals, single crystals or powders, nuclear or magnetic structures, with a unique interface and dirrect support of difractometer output.
	www.fzu.cz /research/cond_systA8.html (510 words)

	Torsti: Real-Space Electronic Structure Calculations for Nanoscale Systems, ISBN 951-22-6470-6
		The electronic transport in atomic chains of a few Na atoms between cone-shaped leads is investigated in the thesis.
		Electrons residing in a Na island on the Cu(111) surface form a quantum dot system, in which the quantum mechanical confinement in all directions determines the electronic properties.
		Electronic resonance states in nanowires during the breaking process simulated with the ultimate jellium model.
	lib.tkk.fi /Diss/2003/isbn9512264706 (509 words)

	Electronic structure (from halogen element) -- Encyclopædia Britannica
		In fine structure (q.v.), line splitting is the result of energy changes produced by electron spin–orbit coupling (i.e., interaction of...
		Social structure is often treated together with the concept of social change, which deals with the forces that change the social structure and the organization of society.
		It is especially concerned with their use in electronic devices, in which electricity is used to control, communicate,...
	www.britannica.com /eb/article-81062?tocId=81062 (883 words)

	Bohr on Electronic Structure of Periodic Table
		A consideration of this law leads directly to the view that the electrons atom are arranged in distinctly separate groups, each containing a number of electrons equal to one of the periods in the sequence of the elements, arranged according to increasing atomic number.
		On the contrary, it seems necessary to seek the configurations of the electrons in the atoms among such configurations as may be formed by the successive binding of the electrons one by one, a process the last stages of which we may assume to witness in the emission of the series spectra of the elements.
		The electrons bound after the first two will not be able by a transition between two stationary states to produce a position in the atom equivalent to that of these two electrons, but will move in what may be called multiple quanta orbits, which correspond to other stationary states of a central system.
	dbhs.wvusd.k12.ca.us /webdocs/Chem-History/Bohr-Nature-1921.html (1296 words)

	Electronic structure (from periodic law) -- Encyclopædia Britannica
		This property would depend upon their possessing especially stable electronic structures (that is, structures so firmly knit that they would not yield to accommodate ordinary chemical bonds).
		According to the older shell atomic model, electrons occupy several levels from the first shell nearest the nucleus, K, through the seventh shell, Q, farthest from the nucleus.
		Electronics is the branch of physics concerned with the generation and behavior of electrons, as in transistors and electron tubes.
	www.britannica.com /eb/article-80840 (828 words)

	atom -> Structure of the Atom on Encyclopedia.com 2002 (Site not responding. Last check: 2007-10-07)
		atom -> Structure of the Atom on Encyclopedia.com 2002
		Surrounding the nucleus of an atom are its electrons; for a neutral atom, the number of electrons is equal to the atomic number.
		As a result the electrons in an atom cannot be pictured as localized in space, but rather should be viewed as smeared out over the entire orbit so that they form a cloud of charge.
	www.encyclopedia.com /html/section/atom_structureoftheatom.asp (857 words)

	Session X34 - Electronic Structure - Insulators.
		The calculated electronic density of states describes satisfactorily the structures of the O 2p- and 2s-like valence bands from the ultraviolet photo-electron (UPS) measurements.^1 The Ba 5p-like bands lead to two DOS peaks at -9.2 eV and -10.2 eV in reasonable agreement with the observed doublet near 12.0 eV from the UPS measurements.
		The unoccupied bulk electronic structure is measured using C 1s near edge x-ray absorption spectroscopy.
		We have calculated the electronic structure, optical properties, and charge distribution of ruthenium dioxide using a self-consistent linear combination of atomic orbitals (LCAO) method and a local density functional potential.
	flux.aps.org /meetings/YR98/BAPSMAR98/abs/S4920.html (2006 words)

	Electronic Structure of Diatomic Molecules
		The simplest diatomic molecular structure is the hydrogen molecule ion, H
		Therefore, when we treat the electronic properties of the molecule, such as the energy of the molecular orbitals, the nuclei can be considered stationary.
		therefore includes the kinetic energy of the electron, the potential energy of repulsion between the two nuclei (a and b) and the attractions between the electron and nuclei 1-a, 1-b.
	www.ubishops.ca /ccc/div/sci/chem/quantum/HAMMOL.html (882 words)

	Electronic Structure and Periodicity
		When itinerant electrons return to such a one-electron bond, the band gap energy can be released as a photon.
		The band gap energy is to a first approximation expected to increase as the bonds become stronger and shorter and the electrons are held more tightly.
		The group 14 elements illustrate this effect with diamond being an electrical insulator, silicon and germanium (longer, weaker bonds in the same diamond structure) being semiconductors, and ap;tin being a metal.
	jce.divched.org /JCEDLib/QBank/collection/ConcepTests/electronh.html (925 words)

	[No title]
		The electron is then transferred from pheophytin to a plastoquinone molecule (QA) that is permanently bound to photosystem II and then onto a second plastoquinone (QB) that becomes fully reduced and protonated after two photochemical turnovers of the reaction center.
		This thesis focuses on the elucidation of the electronic structure of the chlorophyll a cation radical in vitro.
		15,18 The McConnell equation provides a simple linear relationship between the hfi and spin density for most -type organic radicals.15 Knowledge of the spin density of unpaired electrons in a molecule therefore imparts information on the highest occupied molecular orbital (HOMO) of the molecule.
	www.squeep.com /~rockford/Thesis.doc (3068 words)

	ELEMENTARY ELECTRONIC STRUCTURE (Site not responding. Last check: 2007-10-07)
		This is a revised edition of the 1999 text on the electronic structure and properties of solids, similar in spirit to the well-known 1980 text Electronic Structure and the Properties of Solids.
		Such back-of-the-envelope formulae, which display the dependence of any property on the parameters of the system, are characteristic of Harrison's approach to electronic structure, as is his simple presentation and his providing all of the needed parameters.
		In spite of the diversity of systems and materials, the approach is systematic and coherent, combining the tight-binding (or atomic) picture with the pseudopotential (or free-electron) picture.
	www.worldscibooks.com /physics/4121.htm (288 words)

	Physics Today December 2001
		Although a number of electronic structure codes were used in the writing of this book, there is very little reference within the text to specific codes.
		Rather, the authors discuss the principles involved in electronic structure theory at the ab-initio level, and how those principles can be utilized in the derivation and optimization of algorithms for such calculations.
		It is the most complete and satisfying presentation of the actual armament involved in the computational approach to electronic structure that I have seen, and should be available to all students and researchers who wish to understand the basis of contemporary molecular electronic structure methods.
	www.physicstoday.org /pt/vol-54/iss-12/p52a.html (796 words)

	Introduction to electronic structure calculations (Site not responding. Last check: 2007-10-07)
		As a result of recent successes in describing and predicting properties of materials, electronic structure calculations have become increasingly important in the fields of physics and chemistry over the past decade, especially with the advent of present-day, high-performance computers.
		The student will be introduced to computational methods used in electronic structure calculations at various levels of sophistication: tight-binding approximation, density-functional theory, Hartree-Fock methods, etc. Lectures on concepts will be combined with practical exercises designed to enable the student not only to use the various standard codes, but also to develop new ones, if required.
		The relation between the electronic structure of graphite and the nanotube electronic structure.
	webusers.physics.umn.edu /~dnguyen/esctmp.html (432 words)

	Paper 26: Electronic Structure of Solvated Molecular Ions
		We choose ab initio electronic eigenfunctions of the isolated solute molecule as basis functions for a Hamiltonian matrix which describes the effects of the solvent upon the electronic structure of the solute.
		In the electronic excited state however, the charge is displaced in the opposite direction, towards the I end, and the experiments show that this electronic state dissociates adiabatically to an I- anion and a Cl atom.
		Since we are interested in electronic transitions, which are usually thought of as taking place at a fixed nuclear geometry ("Franck-Condon Principle"), we want vertically related points on the ground and excited surfaces to correspond to the same nuclear configuration.
	jarrett.colorado.edu /~rparson/iclminus.html (1594 words)

	Energy Citations Database (ECD) - Energy and Energy-Related Bibliographic Citations
		The electronic structure of two types of hydrogen storage materials has been investigated by ab initio band structure methods.
		The experimentally observed increased stability of aged tritium in a palladium matrix is not entirely due to lattice expansion, which amounts to only 28% of the effect, but also to modifications of the electronic structure in the presence of helium.
		He also discusses the factors that affect the electronic structure and the stability of the hydrides, and compares the results with available experimental data.
	www.osti.gov /energycitations/product.biblio.jsp?osti_id=20020822 (380 words)

	Electronic structure code for very large systems - Nanodot (Site not responding. Last check: 2007-10-07)
		The code computes the electronic density of states of very large samples (in my case up-to nearly 8 million atoms of TiO2).
		Background: The program computes the electronic density of states (local, per atom, per orbital resolved, and total) using the Equation-of-Motion method.
		The program can be used to model very large networks of carbon structures, nanotube networks etc. It was developed for disordered transition metal oxides, where it is often difficult to apply ab-initio methods.
	nanodot.org /article.pl?sid=01/12/18/1548257&mode=thread&threshold= (314 words)

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