Recent Advances In Computational Chemistry – serie

This is a comprehensive overview of state-of-the-art computational methods based on orbital-free formulation of density functional theory completed by the most recent developments concerning the exact properties, approximations, and interpretations of the relevant quantities in density functional theory.The book is a compilation of contributions stemming from a series of workshops which had been taking place since 2002. It not only chronicles many of the latest developments but also summarises some of the more significant ones. The chapters are mainly reviews of sub-domains but also include original research.

Of all the different areas in computational chemistry, density functional theory (DFT) enjoys the most rapid development. Even at the level of the local density approximation (LDA), which is computationally less demanding, DFT can usually provide better answers than Hartree-Fock formalism for large systems such as clusters and solids. For atoms and molecules, the results from DFT often rival those obtained by ab initio quantum chemistry, partly because larger basis sets can be used. Such encouraging results have in turn stimulated workers to further investigate the formal theory as well as the computational methodology of DFT.This volume contains ten contributions from active workers in DFT, covering topics from basic principles to methodology to applications. In the Foreword, Prof Walter Kohn gives his perspective on the recent advances in DFT. Because DFT is being developed in so many different directions, no single volume can provide a complete review of DFT. However, this volume will help both beginners and experimentalists to read the growing DFT literature more easily.

The quantum Monte Carlo (QMC) method is gaining interest as a complement to basis set ab initio methods in cases where high accuracy computation of atomic and molecular properties is desired. This volume focuses on recent advances in this area. QMC as used here refers to methods that directly solve the Schrödinger equation, for example, diffusion and Green's function Monte Carlo, as well as variational Monte Carlo. The latter is an approach to computing atomic and molecular properties by the Monte Carlo method that has fundamental similarities to basis set methods with the exception that the limitation to one-particle basis functions to facilitate integral evaluation is avoided. This feature makes possible the consideration of many-body wave functions containing explicitly interparticle distances — a capability common to all variants of QMC.

Today, coupled-cluster (CC) theory has emerged as the most accurate, widely applicable approach for the correlation problem in molecules. Furthermore, the correct scaling of the energy and wavefunction with size (i.e. extensivity) recommends it for studies of polymers and crystals as well as molecules. CC methods have also paid dividends for nuclei, and for certain strongly correlated systems of interest in field theory.In order for CC methods to have achieved this distinction, it has been necessary to formulate new, theoretical approaches for the treatment of a variety of essential quantities. These include properties and, particularly, analytical first derivatives (gradients) that readily provide the forces on the atoms in a molecule to facilitate searching potential energy surfaces for structures and transition states; second derivatives (Hessians) which indicate the type of extremum point and provide vibrational frequencies and intensities; excited, ionized, and electron attached states including their properties; multi-configurational reference functions to add important non-dynamic correlation; and relativistic effects.This book addresses very recent work in each of the above topics in ten chapters written by leading experts in molecular CC theory. This is NOT a collection of reviews, but is, instead, forefront research explained in an unusually clear exposition. Each chapter presents new results and formulations that offer another step toward providing the next generation of powerful CC solutions.The gap that often exists between text books and research can be more of a chasm in highly technical fields like CC theory, but this volume helps to fill the void, as it provides a sequel to a graduate level course in CC theory and many-electron methods. Essentially all current directions for new research are well represented in the authoritative articles.

Of all the different areas in computational chemistry, density functional theory (DFT) enjoys the most rapid development. Even at the level of the local density approximation (LDA), which is computationally less demanding, DFT can usually provide better answers than Hartree-Fock formalism for large systems such as clusters and solids. For atoms and molecules, the results from DFT often rival those obtained by ab initio quantum chemistry, partly because larger basis sets can be used. Such encouraging results have in turn stimulated workers to further investigate the formal theory as well as the computational methodology of DFT.This Part II expands on the methodology and applications of DFT. Some of the chapters report on the latest developments (since the publication of Part I in 1995), while others extend the applications to wider range of molecules and their environments. Together, this and other recent review volumes on DFT show that DFT provides an efficient and accurate alternative to traditional quantum chemical methods. Such demonstration should hopefully stimulate frutiful developments in formal theory, better exchange-correlation functionals, and linear scaling methodology.

Of all the different areas in computational chemistry, density functional theory (DFT) enjoys the most rapid development. Even at the level of the local density approximation (LDA), which is computationally less demanding, DFT can usually provide better answers than Hartree-Fock formalism for large systems such as clusters and solids. For atoms and molecules, the results from DFT often rival those obtained by ab initio quantum chemistry, partly because larger basis sets can be used. Such encouraging results have in turn stimulated workers to further investigate the formal theory as well as the computational methodology of DFT.This Part II expands on the methodology and applications of DFT. Some of the chapters report on the latest developments (since the publication of Part I in 1995), while others extend the applications to wider range of molecules and their environments. Together, this and other recent review volumes on DFT show that DFT provides an efficient and accurate alternative to traditional quantum chemical methods. Such demonstration should hopefully stimulate frutiful developments in formal theory, better exchange-correlation functionals, and linear scaling methodology.

Recently, accurate ab initio quantum computational chemistry has evolved dramatically. In particular, the development of multireference-based approaches has opened up a whole new area and has also had a profound impact on the potential of theoretical chemistry.The multiconfigurational SCF (MCSCF)/CASSCF method is an attempt to generalize the Hartree-Fock (HF) model and to treat real chemical processes, where nondynamic correlation is important, while keeping the conceptual simplicity of the HF model as much as possible. Although MCSCF/CASSCF itself does not include dynamic correlations, it provides a good starting point for such studies. There are three approaches to handling dynamic correlations. Beginning with the MSSCF/CASSCF wave function, they are the variational (MRCI), perturbational (MRPT) and cluster expansion (MRCC) approaches.This important book presents the most recent and important developments in multireference-based approaches and their applications. Its main purpose is to highlight essential aspects of the frontiers of multireference theory and provide readers with the fundamental knowledge necessary for further development.

In the last few years, much attention has been given by theoretical chemists to the development of more accurate model functionals and faster computational techniques including excited electronic states. The 8th International Conference on the Applications of Density Functional Theory to Chemistry and Physics, held in Rome, Italy, on 6-10 September 1999, gathered chemists and physicists to present and discuss state-of-the-art methodological developments and applications of density functional theory (DFT) to increasingly complex systems. The scientists shared their knowledge and experience in DFT, enabling them to face the challenges posed by the needs of high level modeling and simulation in their disciplines. The meeting was opened with an exciting lecture delivered by Nobel laureate W Kohn.The growing use of DFT in studying organic, inorganic and organometallic molecules, clusters and solids provided the basis for the success of the conference, whose main contributions are collected in this invaluable book.

This invaluable book consists of 16 chapters written by some of the most notable researchers in the field of quantum Monte Carlo, highlighting the advances made since Lester Jr.'s 1997 monograph with the same title. It may be regarded as the proceedings of the Symposium on Advances in Quantum Monte Carlo Methods held during the Pacifichem meeting in December 2000, but the contributions go beyond what was presented there.