QUANTUM CHEMISTRY – MOLECULES FOR INNOVATIONS Edited by Tomofumi Tada Quantum Chemistry – Molecules for Innovations Edited by Tomofumi Tada Published by InTech Janeza Trdine 9, 51000 Rijeka, Croatia Copyright © 2012 InTech All chapters are Open Access distributed under the Creative Commons Attribution 3.0 license, which allows users to download, copy and build upon published articles even for commercial purposes, as long as the author and publisher are properly credited, which ensures maximum dissemination and a wider impact of our publications. After this work has been published by InTech, authors have the right to republish it, in whole or part, in any publication of which they are the author, and to make other personal use of the work. Any republication, referencing or personal use of the work must explicitly identify the original source. As for readers, this license allows users to download, copy and build upon published chapters even for commercial purposes, as long as the author and publisher are properly credited, which ensures maximum dissemination and a wider impact of our publications. Notice Statements and opinions expressed in the chapters are these of the individual contributors and not necessarily those of the editors or publisher. No responsibility is accepted for the accuracy of information contained in the published chapters. The publisher assumes no responsibility for any damage or injury to persons or property arising out of the use of any materials, instructions, methods or ideas contained in the book. Publishing Process Manager Sasa Leporic Technical Editor Teodora Smiljanic Cover Designer InTech Design Team First published March, 2012 Printed in Croatia A free online edition of this book is available at www.intechopen.com Additional hard copies can be obtained from orders@intechopen.com Quantum Chemistry – Molecules for Innovations, Edited by Tomofumi Tada p. cm. ISBN 978-953-51-0372-1 Contents Preface IX Part 1 Theories in Quantum Chemistry 1 Chapter 1 Numerical Solution of Linear Ordinary Differential Equations in Quantum Chemistry by Spectral Method 3 Masoud Saravi and Seyedeh-Razieh Mirrajei Chapter 2 Composite Method Employing Pseudopotential at CCSD(T) Level 11 Nelson Henrique Morgon Part 2 Electronic Structures and Molecular Properties 23 Chapter 3 Quantum Chemical Calculations for some Isatin Thiosemicarbazones 25 Fatma Kandemirli, M. Iqbal Choudhary, Sadia Siddiq, Murat Saracoglu, Hakan Sayiner, Taner Arslan, Ayşe Erbay and Baybars Köksoy Chapter 4 Elementary Molecular Mechanisms of the Spontaneous Point Mutations in DNA: A Novel Quantum-Chemical Insight into the Classical Understanding 59 Ol'ha O. Brovarets’, Iryna M. Kolomiets’ and Dmytro M. Hovorun Chapter 5 Quantum Chemistry and Chemometrics Applied to Conformational Analysis 103 Aline Thaís Bruni and Vitor Barbanti Pereira Leite Part 3 Molecules to Nanodevices 131 Chapter 6 Quantum Transport and Quantum Information Processing in Single Molecular Junctions 133 Tomofumi Tada VI Contents Chapter 7 Charge Carrier Mobility in Phthalocyanines: Experiment and Quantum Chemical Calculations 159 Irena Kratochvilova Chapter 8 Theoretical Study for High Energy Density Compounds from Cyclophosphazene 175 Kun Wang, Jian-Guo Zhang, Hui-Hui Zheng, Hui-Sheng Huang and Tong-Lai Zhang Preface Molecules, small structures composed of atoms, are essential substances for lives. However, we didn’t have the clear answer to the following questions until the 1920s: why molecules can exist in stable as rigid networks between atoms, and why molecules can change into different types of molecules. The most important event for solving the puzzles is the discovery of the quantum mechanics. Quantum mechanics is the theory for small particles such as electrons and nuclei, and was applied to hydrogen molecule by Heitler and London at 1927. The pioneering work led to the clear explanation of the chemical bonding between the hydrogen atoms. This is the beginning of the quantum chemistry. Since then, quantum chemistry has been an important theory for the understanding of molecular properties such as stability, reactivity, and applicability for devices. Quantum chemistry has now two main styles: (i) the precise picture (computations) and (ii) simple picture (modeling) for describing molecular properties. Since the Schrodinger equation, the key differential equation in quantum mechanics, cannot be solved for polyatomic molecules in the original many-body form, some approximations are required to apply the equation to molecules. A popular strategy is the approximation of the many-body wave functions by using single-particle wave functions in a single configuration. The single-particle wave function can be represented with the linear combination of atomic orbitals (LCAOs), and the differential equation to be solved is consequently converted to a matrix form, in which matrices are written in AO basis. This strategy immediately leads to the Hartree-Fock Roothaan equation, and this is an important branching point toward the precise computations or appropriate modeling. Since the approximations made in the Hartree- Fock Roothaan equation can be clearly recognized, the descriptions of many-body wave functions are expected to be better and better by using much more AOs, multi- configurations, and more rigorous treatment for many-body interactions. Prof. J. A. Pople was awarded the Novel prize in Chemistry at 1998 for his pioneering works devoted for the development of the wave function theory toward the precise picture of molecular properties. The style is of course quite important, especially when we roughly know what are the interesting properties in a target molecule, because our efforts in those cases must be made to obtain more quantitative description of the target properties. However, when we don’t know what the interesting properties of X Preface the target molecule are, we have to take care whether a quantum chemical method in your hand is really appropriate for your purpose because an expensive method using many AOs and configurations sometimes falls into a difficulty in the extraction of the intrinsic property of the target molecule. Thus, we have to turn to the second style, the simple picture, to capture the properties of the target molecule roughly. For example, a simple π orbital picture is useful to predict the reactivity of π organic molecules on the basis of the frontier orbital theory in which the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) are the key orbitals for the prediction of the chemical response of the target molecule. When symbolized AOs (i.e., AOs represented neither in analytical nor in numerical form) are adopted for calculations, the Hamiltonian matrix is simply represented only with the numbers “0” and “1”. Despite the simple description for the molecule, the frontier orbitals calculated (sometimes by hand) from the Hamiltonian are quite effective for the prediction of the reactivity of the target molecule. Prof. K. Fukui, the pioneer of the frontier orbital theory, was awarded the Novel prize in Chemistry at 1981. Nowadays, our target molecules are structured as more diverse atomic networks and embedded in more complicated environment. The molecular properties are thus inevitably dependent on the complicated situations, and therefore we need the balanced combination of both styles, simple-and-precise picture, for the target today. We have to consider how we should build the veiled third style. To keep this in mind, this book is composed of nine chapters for the quantum chemical theory, conventional applications and advanced applications. I sincerely apologize this book cannot cover the broad spectrum of quantum chemistry. However, I hope this book, Quantum Chemistry – Molecules for Innovation, will be a hint for younger generations. Tomofumi Tada Global COE for Mechanical Systems Innovation, Department of Materials Engineering, The University of Tokyo, Japan . QUANTUM CHEMISTRY – MOLECULES FOR INNOVATIONS Edited by Tomofumi Tada Quantum Chemistry – Molecules for Innovations Edited by Tomofumi. orders@intechopen.com Quantum Chemistry – Molecules for Innovations, Edited by Tomofumi Tada p. cm. ISBN 978-953-51-0372-1 Contents Preface IX Part 1 Theories in Quantum Chemistry. the quantum chemistry. Since then, quantum chemistry has been an important theory for the understanding of molecular properties such as stability, reactivity, and applicability for devices. Quantum