Mueller M.R. - Fundamentals of Quantum Chemistry[c] Molecular Spectroscopy and Modern Electronic Structure Computations (Kluwer, 2001)

Fundamentals of

Quantum Chemistry

This page intentionally left blank

©2002 Kluwer Academic Publishers

New York, Boston, Dordrecht, London, Moscow

Print ©2001 Kluwer Academic/Plenum Publishers

New York

All rights reserved

No part of this eBook may be reproduced or transmitted in any form or by any means, electronic, mechanical, recording, or otherwise, without written consent from the Publisher

Created in the United States of America

vi Foreword

in the low infrared region! Post World War II advances in instrumentation, particularly the spin-offs of the National Aeronautics and Space Administration (NASA) efforts, quickly changed the landscape of highresolution spectroscopic data. Laser sources and Fourier transform spectroscopy are two notable advances, and these began to appear in undergraduate laboratories in the mid-1980s. At that time, only chemists with access to supercomputers were to realize the full fruits of quantum theory. This past decade’s advent of commercially available quantum mechanical calculation packages, which run on surprisingly sophisticated laptop computers, provide approximation technology for all chemists. Approximation techniques developed by the early pioneers can now be carried out to as many iterations as necessary to produce meaningful results for sophomore organic chemistry students, graduate students, endowed chair professors, and pharmaceutical researchers. The impact of quantum mechanical calculations is also being felt in certain areas of the biological sciences, as illustrated in the results of conformational studies of biologically active molecules. Today’s growth of quantum chemistry literature is as fast as that of NMR studies in the 1960s.

An excellent example of the introduction of quantum chemistry calculations in the undergraduate curriculum is found at the author’s institution. Sophomore organic chemistry students are introduced to the PCSpartan+® program to calculate the lowest energy of possible structures. The same program is utilized in physical chemistry to compute the potential energy surface of the reaction coordinate in simple reactions. Biochemistry students take advantage of calculations to elucidate the pathways to creation of designer drugs. This hands-on approach to quantum chemistry calculations is not unique to that institution. However, the flavor of the department’s philosophy ties in quite nicely with the tone of this textbook that is pitched at just the proper level, advanced undergraduates and first year graduate students.

Farrell Brown

Professor Emeritus of Chemistry

Clemson University

Preface

This text is designed as a practical introduction to quantum chemistry for undergraduate and graduate students. The text requires a student to have completed a year of calculus, a physics course in mechanics, and a minimum of a year of chemistry. Since the text does not require an extensive background in chemistry, it is applicable to a wide variety of students with the aforementioned background; however, the primary target of this text is for undergraduate chemistry majors.

The text provides students with a strong foundation in the principles, formulations, and applications of quantum mechanics in chemistry. For some students, this is a terminal course in quantum chemistry providing them with a basic introduction to quantum theory and problem solving techniques along with the skills to do electronic structure calculations - an application that is becoming increasingly more prevalent in all disciplines of chemistry. For students who will take more advanced courses in quantum chemistry in either their undergraduate or graduate program, this text will provide a solid foundation that they can build further knowledge from.

Early in the text, the fundamentals of quantum mechanics are established. This is done in a way so that students see the relevance of quantum mechanics to chemistry throughout the development of quantum theory through special boxes entitled Chemical Connection. The questions in these boxes provide an excellent basis for discussion in or out of the classroom while providing the student with insight as to how these concepts will be used later in the text when chemical models are actually developed.

vii

viii Preface

Students are also guided into thinking “quantum mechanically” early in the text through conceptual questions in boxes entitled Points of Further Understanding. Like the questions in the Chemical Connection boxes, these questions provide an excellent basis for discussion in or out of the classroom. These questions move students from just focusing on the rigorous mathematical derivations and help them begin to visualize the implications of quantum mechanics.

Rotational and vibrational spectroscopy of molecules is discussed in the text as early as possible to provide an application of quantum mechanics to chemistry using model problems developed previously. Spectroscopy provides for a means of demonstrating how quantum mechanics can be used to explain and predict experimental observation.

The last chapter of the text focuses on the understanding and the approach to doing modern day electronic structure computations of molecules. These types of computations have become invaluable tools in modern theoretical and experimental chemical research. The computational methods are discussed along with the results compared to experiment when possible to aide in making sound decisions as to what type of Hamiltonian and basis set that should be used, and it provides a basis for using computational strategies based on desired reliability to make computations as efficient as possible.

There are many people to thank in the development of this text, far too many to list individually here. A special thanks goes out to the students over the years who have helped shape the approach used in this text based on what has helped them learn and develop interest in the subject.

Terre Haute, IN Michael R. Mueller