Electronics foundations

Joseph W. Tringe Lead, Electronics Foundation Research Group Space Vehicles Directorate Air Force Research Laboratory... 

Although a separation of electronic and nuclear motion provides an important simplification and appealing qualitative model for chemistry, the electronic Sclirodinger equation is still fomiidable. Efforts to solve it approximately and apply these solutions to the study of spectroscopy, stmcture and chemical reactions fonn the subject of what is usually called electronic structure theory or quantum chemistry. The starting point for most calculations and the foundation of molecular orbital theory is the independent-particle approximation. 

In this chapter, the foundations of equilibrium statistical mechanics are introduced and applied to ideal and weakly interacting systems. The coimection between statistical mechanics and thennodynamics is made by introducing ensemble methods. The role of mechanics, both quantum and classical, is described. In particular, the concept and use of the density of states is utilized. Applications are made to ideal quantum and classical gases, ideal gas of diatomic molecules, photons and the black body radiation, phonons in a hannonic solid, conduction electrons in metals and the Bose—Einstein condensation. Introductory aspects of the density... 

This theoretical foundation of electron diffraction as given by Wierl [26] and modification of this equation partly following suggestions made by Soltzberg and Wilkins [27] gives Eq. (24), with the atomic property p for the atoms i and j, a reciprocal distance s, and the distance tu between the atoms i and j. 

The most notable studies are those of Ingold, on the orienting and activating properties of substituents in the benzene nucleus, and of Dewar on the reactivities of an extensive series of polynuclear aromatic and related compounds ( 5.3.2). The former work was seminal in the foundation of the qualitative electronic theory of the relationship between structure and reactivity, and the latter is the most celebrated example of the more quantitative approaches to the same relationship ( 7.2.3). Both of the series of investigations employed the competitive method, and were not concerned with the kinetics of reaction. 

Electron microscopy studies were performed at the Centre Interdepartamental de Microscopie Electronique (CIME), Ecole Polytechnique Fdddrale de Lausanne. We are grateful to the Brazilian Council for Scientific and Technologic Research (CNPq) and the Swiss National Science Foundation for financial support. 

TT-Electron materials, which are defined as those having extended Jt-electron clouds in the solid state, have various peculiar properties such as high electron mobility and chemical/biological activities. We have developed a set of techniques for synthesizing carbonaceous K-electron materials, especially crystalline graphite and carbon nanotubes, at temperatures below 1000°C. We have also revealed new types of physical or chemical interactions between Jt-electron materials and various other materials. The unique interactions found in various Jt-electron materials, especially carbon nanotubes, will lay the foundation for developing novel functional, electronic devices in the next generation. 

With this foundation, Boger communicated the use of 1,2,4-triazines as a dependable, azadiene equivalent for Diels-Alder approaches to substituted pyridines. Electron rich olefin 19, prepared from the corresponding ketone, was allowed to... 

Institute of Electronic Structure and Laser, Foundation for Research and Technology-HeUas, P.O. Box 1527, Herakho, Crete, Greece 71110 Physics Department, University of Crete, P.O. Box 1470, Herakho,Greece 71409 Department of Physics and Astronomy, and Center for Computational Sciences, University of Kentucky, Lexington, KY 40506-0055... 

Institute of Electronic Structure and Laser,Foundation for Research and... 

Prof. A. N. Andriotis Institute of Electronic Structure and Laser Foundation of Research and Technology-Hellas PO Box 1527 Heraklion, 71110 Crete Greece... 

This paper deals with some questions in the foundations of chemistry. The atomic orbital (or electronic configuration) model is examined, with regards to both its origins and current usage. I explore the question of whether the commonly-used electronic configuration of atoms have any basis in quantum mechanics as is often claimed particularly in chemical education. 

ABSTRACT This article concerns various foundational aspects of the periodic system of the elements. These issues include the dual nature of the concept of an "element" to include element as a "basic substance" and as a "simple substance." We will discuss the question of whether there is an optimal form of the periodic table, including whether the left-step table fulfils this role. We will also discuss the derivation or explanation of the [n + , n] or Madelung rule for electron-shell filling and whether indeed it is important to attempt to derive this rule from first principles. In particular, we examine the views of two chemists, Henry Bent and Eugen Schwarz, who have independently addressed many of these issues. 2008 Wiley Periodicals, Inc. Int J Quantum Chem 109 959-971, 2009... 

The suggestion of the present author is more radical. It is suggested that both of these rules, n + f for neutral atoms and the rule of increasing n for bonded atoms, are somewhat irrelevant in the question of the foundations of the periodic system. This is because chemical identity resides at the level of the nucleus and therefore with atomic number, and not at the ever-changing level of electrons whose configuration is summarized by the aforementioned rules.14... 

For systems containing three or more electrons very little is so far known about the foundation for the method of correlated wave functions, and research on this problem would be highly desirable. It seems as if one could expect good energy results by means of a wave function being a product of a properly scaled Hartree-Fock function and a correlation factor" containing the interelectronic distances ru (Krisement 1957), but too little is known about the limits of accuracy of such an approach. 

PCSs are systems of chromophores bound into a single macromolecule. Therefore, the study of processes of electronic excitation and energy transfer, as well as the investigation of the ways of deactivation of excited states, should lay a foundation for the understanding of such properties of PCSs as reactivity in photochemical transformations, photosensitizing and photoelectric activity, photoinitiated paramagnetism, etc. 

In recent years the old quantum theory, associated principally with the names of Bohr and Sommerfeld, encountered a large number of difficulties, all of which vanished before the new quantum mechanics of Heisenberg. Because of its abstruse and difficultly interpretable mathematical foundation, Heisenberg s quantum mechanics cannot be easily applied to the relatively complicated problems of the structures and properties of many-electron atoms and of molecules in particular is this true for chemical problems, which usually do not permit simple dynamical formulation in terms of nuclei and electrons, but instead require to be treated with the aid of atomic and molecular models. Accordingly, it is especially gratifying that Schrodinger s interpretation of his wave mechanics3 provides a simple and satisfactory atomic model, more closely related to the chemist s atom than to that of the old quantum theory. 

All of the optical and infrared focal plane arrays are solid state electronic devices, and to fully understand their physics and operation, one should have a solid foundation in the solid state electronics. An excellent reference is ... 

The concept of an octet of electrons is one of the foundations of chemical bonding. In fact, C, N, and O, the three elements that occur most frequently in organic and biological molecules, rarely stray from the pattern of octets. Nevertheless, an octet of electrons does not guarantee that an inner atom is in its most stable configuration. In particular, elements that occupy the third and higher rows of the periodic table and have more than four valence electrons may be most stable with more than an octet of electrons. Atoms of these elements have valence d orbitals, which allow them to accommodate more than eight electrons. In the third row, phosphoms, with five valence electrons, can form as many as five bonds. Sulfur, with six valence electrons, can form six bonds, and chlorine, with seven valence electrons, can form as many as seven bonds. 

Because electrons have wave-like properties, orbital interactions involve similar addition or subtraction of wave functions. When two orbitals are superimposed, one result is a new orbital that is a composite of the originals, as shown for molecular hydrogen in Figure 10-2. This interaction is called orbital overlap, and it is the foundation of the bonding models described in this chapter. 

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