Semi-empirical Self-consistent-field Molecular Orbital Theory of Molecules PDF Download
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Author: John Norman Murrell
Publisher:
ISBN: 9780608176758
Category :
Languages : en
Pages : 180
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Book Description
Author: John Norman Murrell
Publisher:
ISBN: 9780608176758
Category :
Languages : en
Pages : 180
Get Book Here
Book Description
Author: J.N. Murrell
Publisher:
ISBN:
Category :
Languages : en
Pages : 180
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Book Description
Author: G.H. Wagniere
Publisher: Springer Science & Business Media
ISBN: 3642930506
Category : Science
Languages : en
Pages : 114
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Book Description
These notes summarize in part lectures held regularly at the University of Zurich and, in the Summer of 1974, at the Semi nario Latinoamericano de QUimica Cuantica in Mexico. I am grateful to those who have encouraged me to publish these lec tures or have contributed to them by their suggestions. In particular, I wish to thank Professor J. Keller of the Univer sidad Nacional Autonoma in Mexico, Professor H. Labhart and Professor H. Fischer of the University of Zurich, as well as my former students Dr. J. Kuhn, Dr. W. Hug and Dr. R. Geiger. The aim of these notes is to provtde a summary and concise introduction to elementary molecular orbital theory, with an emphasis on semiempirical methods. Within the last decade the development and refinement of ab initio computations has tended to overshadow the usefulness of semiempirical methods. However, both approaches have their justification. Ab initio methods are designed for accurate predictions, at the expense of greater computational labor. The aim of semiempirical methods mainly lies in a semiquantitative classification of electronic pro perties and in the search for regularities within given classes of larger molecules. The reader is supposed to have had some previous basic instruc tion in quantum mechanics, such as is now offered in many uni versities to chemists in their third or fourth year of study. The bibliography should encourage the reader to consult other texts, in particular also selected publications in scientific journals.
Author: John Norman Murrell
Publisher: John Wiley & Sons
ISBN:
Category : Science
Languages : en
Pages : 200
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Book Description
Author: Einar Lindholm
Publisher: Springer Science & Business Media
ISBN: 3642455956
Category : Science
Languages : en
Pages : 301
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Book Description
This treatment of molecular and atomic physics is primarily meant as a textbook. It is intended for both chemists and physicists. ·It can be read without much knowledge of quantum mechanics or mathematics, since all such details are explained-. It has developed through a series of lectures at the Royal Institute of Technology. The content is to about 50 % theoretical and to 50 % experimental. The reason why the authors, who are experimentalists, went into theory is the following. When we during the beginning of the 1970's measured photo electron spectra of organic molecules, it appeared to be impossible to understand them by use of available theoretical calculations. To handle hydrocarbons we ( together with C. Fridh ) constructed in 1972 a purely empirical procedure, SPINDO [1] which has proved to be useful, but the extension to molecules with hetero atoms appeared to be difficult. One of us ( L.A.) proposed then another purely ~~E!E!~~! EE2~~~~E~ ( Hydrogenic Atoms in Molecules, HAM/1, unpublished), in which the Fock matrix elements f5..y were parametrized using Slater's shielding concept. The self-repulsion was compensated by a term "-1". The §~~2~~_~ff2E~, HAM/2 [2] , started from the total energy E:. of the molecule. The atomic parts of L used the Slater shielding constants, and the bond parts of E. were taken from SPINDO. The Fock matrix elements Fpv were then obtained from E in a conventional way.
Author: Gerald Segal
Publisher: Springer Science & Business Media
ISBN: 1468425560
Category : Science
Languages : en
Pages : 285
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Book Description
If one reflects upon the range of chemical problems accessible to the current quantum theoretical methods for calculations on the electronic structure of molecules, one is immediately struck by the rather narrow limits imposed by economic and numerical feasibility. Most of the systems with which experimental photochemists actually work are beyond the grasp of ab initio methods due to the presence of a few reasonably large aromatic ring systems. Potential energy surfaces for all but the smallest molecules are extremely expensive to produce, even over a restricted group of the possible degrees of freedom, and molecules containing the higher elements of the periodic table remain virtually untouched due to the large numbers of electrons involved. Almost the entire class of molecules of real biological interest is simply out of the question. In general, the theoretician is reduced to model systems of variable appositeness in most of these fields. The fundamental problem, from a basic computational point of view, is that large molecules require large numbers of basis functions, whether Slater type orbitals or Gaussian functions suitably contracted, to provide even a modestly accurate description of the molecular electronic environment. This leads to the necessity of dealing with very large matrices and numbers of integrals within the Hartree-Fock approximation and quickly becomes both numerically difficult and uneconomic.
Author: Gerald Maurice Maggiora
Publisher:
ISBN:
Category :
Languages : en
Pages : 316
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Book Description
Author: John Norman Murrell
Publisher:
ISBN:
Category :
Languages : en
Pages : 180
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Book Description
Author: Jean-Louis Calais
Publisher: Springer Science & Business Media
ISBN: 9401102635
Category : Science
Languages : en
Pages : 269
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Book Description
The rivers run into the sea, yet the sea is not full Ecclesiastes What is quantum chemistry? The straightforward answer is that it is what quan tum chemists do. But it must be admitted, that in contrast to physicists and chemists, "quantum chemists" seem to be a rather ill-defined category of scientists. Quantum chemists are more or less physicists (basically theoreticians), more or less chemists, and by and large, computationists. But first and foremost, we, quantum chemists, are conscious beings. We may safely guess that quantum chemistry was one of the first areas in the natural sciences to lie on the boundaries of many disciplines. We may certainly claim that quantum chemists were the first to use computers for really large scale calculations. The scope of the problems which quantum chemistry wishes to answer and which, by its unique nature, only quantum chemistry can answer is growing daily. Retrospectively we may guess that many of those problems meet a daily need, or are say, technical in some sense. The rest are fundamental or conceptual. The daily life of most quantum chemists is usually filled with grasping the more or less technical problems. But it is at least as important to devote some time to the other kind of problems whose solution will open up new perspectives for both quantum chemistry itself and for the natural sciences in general.
Author: R. Gandour
Publisher: Springer Science & Business Media
ISBN: 1468499785
Category : Science
Languages : en
Pages : 625
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Book Description
The transItIOn-state theory has been, from the point of its inception, the most influential principle in the development of our knowledge of reaction mechanisms in solution. It is natural that as the field of biochemical dynamics has achieved new levels of refinement its students have increasingly adopted the concepts and methods of transition-state theory. Indeed, every dynamical problem of biochemistry finds its most elegant and economical statement in the terms of this theory. Enzyme catalytic power, for example, derives from the interaction of enzyme and substrate structures in the transition state, so that an understanding of this power must grow from a knowledge of these structures and interactions. Similarly, transition-state interactions, and the way in which they change as protein structure is altered, constitute the pivotal feature upon which molecular evolution must turn. The complete, coupled dynamical system of the organism, incorporating the transport of matter and energy as well as local chemical processes, will eventually have to yield to a description of its component transition-state structures and their energetic response characteristics, even if the form of the description goes beyond present-day transition-state theory. Finally, the importance of biochemical effectors in medicine and agriculture carries the subject into the world of practical affairs, in the use of transition-state information for the construction of ultra potent biological agents.
