Vast progress in the area of computational chemistry has been achieved in the last decade. Theoretical methods such as quantum mechanics, molecular dynamics and statistical mechanics have been successfully used to characterize chemical systems and to design new materials, drugs and chemicals. The reviews presented in this volume discuss the current advances in computational methodologies and their applications. The areas covered include materials science, nanotechnology, inorganic and biological systems. The major thrust of the book is to bring timely overviews of new findings and methods applied in the rapidly changing field of computational chemistry.

There have been important developments in the last decade: computers are faster and more powerful, code features are enhanced and more efficient, and larger molecules can be studied — not only in vacuum but also in a solvent or in crystal. Researchers are using new techniques to study larger systems and obtain more accurate results. This is impetus for the development of more efficient methods based on the first-principle multi-level simulations appropriate for complex species.Among the cutting-edge methods and studies reviewed in this decennial volume of the series are the Density Functional Theory (DFT) method, vibrational electron energy loss spectroscopy (EELS), computational models of the reaction rate theory, the nuclear magnetic resonance triplet wavefunction model (NMRTWM) and biological reactions that benefit from computational studies.

There are strong indications that, in the 21st century, computational chemistry will be a prime research tool not only for the basic sciences but also for the life and materials sciences. Recent developments in nanotechnology allow us to detect a layer of single atoms. Researchers are able not only to image but also to manipulate molecules and atoms. It does not take much imagination to realize that before performing such a task on a real system it is much easier and faster to study models on computers. That is the aim of this volume — it provides up-to-date reviews which cover representative areas of computational chemistry.In Chapter 1, Y Ishikawa and M J Vilkas provide a review of multireference Moller-Plesset (MR-MP) perturbation theory. Fifteen years ago Roberto Car of Princeton University and Michele Parrinello of Max Planck Institute introduced a method that revolutionized electronic structure calculations for molecules, liquids and solids. Ursula Rothlisberger, a former member of Parrinello's group, reviews the formation of the method in its most common implementations in Chapter 2. In the third chapter, Isaac B Bersuker describes the general theory of the combined quantum mechanics-molecular mechanics (QM/MM) approach. In Chapter 4, Marcel Allavena and David White present a review of applications of computational chemistry to proton transfer, the primary process for acid-base chemistry on zeolites. Chapter 5 is a review by S Roszak and J Leszczynski of recent data on the clusters formed from the charged ion and weakly interacting ligands. The last chapter, contributed by Carlos R Handy, is devoted to recent developments in the incorporation of continuous wavelet transform analysis into quantum operator theory.

The gap between experimental objects and models for calculations in chemistry is being bridged. The size of experimental nano-objects is decreasing, while reliable calculations are feasible for larger and larger molecular systems. The results of these calculations for isolated molecules are becoming more relevant for experiments. However, there are still significant challenges for computational methods. This series of books presents reviews of current advances in computational methodologies and applications.Chapter 1 of this volume provides an overview of the theoretical and numerical aspects in the development of the polarizable continuum model (PCM). Chapter 2 demonstrates a multiplicative scheme used to estimate the properties of two- and three-dimensional clusters from the properties of their one-dimensional components. Chapter 3 discusses the application of ab initio methods for a reliable evaluation of the characteristics of hydrogen-bonded and van der Waals complexes.Ab initio quantum-chemical methods are popular among researchers investigating various aspects of DNA. The properties of DNA base polyads linked by base-base hydrogen bonds are reviewed in Chapter 4, while Chapter 5 reviews the primary radiation-induced defects in nucleic acid building blocks, and how DNA can be influenced by chemical and environmental effects. Finally, Chapter 6 discusses available experimental data of DNA bases, base pairs, and their complexes with water.

For the first time in the history of chemical sciences, theoretical predictions have achieved the level of reliability that allows them to - val experimental measurements in accuracy on a routine basis. Only a decade ago, such a statement would be valid only with severe qualifi- tions as high-level quantum-chemical calculations were feasible only for molecules composed of a few atoms. Improvements in both hardware performance and the level of sophistication of electronic structure me- ods have contributed equally to this impressive progress that has taken place only recently. The contemporary chemist interested in predicting thermochemical properties such as the standard enthalpy of formation has at his disposal a wide selection of theoretical approaches, differing in the range of app- cability, computational cost, and the expected accuracy. Ranging from high-level treatments of electron correlation used in conjunction with extrapolative schemes to semiempirical methods, these approaches have well-known advantages and shortcomings that determine their usefulness in studies of particular types of chemical species. The growing number of published computational schemes and their variants, testing sets, and performance statistics often makes it difficult for a scientist not well versed in the language of quantum theory to identify the method most adequate for his research needs.

Hydrogen bonded systems play an important role in all aspects of science but particularly chemistry and biology. Notably, the helical structure of DNA is heavily reliant on the hydrogens bonds between the DNA base pairs. Although the area of hydrogen bonding is one that is well established, our understanding has continued to develop as the power of both computational and experimental techniques has improved. Understanding Hydrogen Bonds presents an up-to-date overview of our theoretical and experimental understanding of the hydrogen bond. Well-established and novel approaches are discussed, including quantum theory of ‘atoms in molecules’ (QTAIM); the electron localization function (ELF) method and Car–Parinnello molecular dynamics; the natural bond orbital (NBO) approach; and X-ray and neutron diffraction and spectroscopy. The mechanism of hydrogen bond formation is described and comparisons are made between hydrogen bonds and other types of interaction. The author also takes a look at new types of interaction that may be classified as hydrogen bonds with a focus on those with multicentre proton acceptors or with multicentre proton donors. Understanding Hydrogen Bonds is a valuable reference for experimentalists and theoreticians interested in updating their understanding of the types of hydrogen bonds, their role in chemistry and biology, and how they can be studied.

Computational methods, and in particular quantum chemistry, have taken the lead in our growing understanding of noncovalent forces, as well as in their categorization. This volume describes the current state of the art in terms of what we now know, and the current questions requiring answers in the future. Topics range from very strong (ionic) to very weak (CH--π) interactions. In the intermediate regime, forces to be considered are H-bonds, particularly CH--O and OH--metal, halogen, chalcogen, pnicogen and tetrel bonds, aromatic stacking, dihydrogen bonds, and those involving radicals. Applications include drug development and predictions of crystal structure.