Recent Progress in Coupled Cluster Methods

The recent progress and future trends in coupled cluster methodology are presented in this comprehensive overview. Written by practitioners in the field, each chapter emphasizes both fundamentals and related methodology in an accessible style and format.

I feel very honored that I have been asked to write a Foreword to this book. The subject of the book - "Coupled cluster theory" - has been around for about half a century. The basic theory and explicit equations for closed-shell ground states were formulated before 1970. At the beginning of the seventies the rst ab initio calcu- tion were carried out. At that time speed and memory of computers were very limited compared to today's standards. Moreover, the size of one-electron bases employed was small, so that it was only possible to achieve an orientation in methodical aspects rather than to generate new signi cant results. Extensive use of the coupled-cluster method started at the beginning of the eighties. With the help of more powerful computers the results of coupled-cluster approaches started to yield more and more interesting results of relevance to the interpretation of experimental data. New ideas in methodology kept appearing and computer codes became more and more ef cient. This exciting situation continues to this very day. Remarkably enough, even the - quired equations can now be generated by a computer with the help of symbolic languages. The size of this monograph and the rich variety of articles it contains attests to the usefulness and viability of the couple-cluster formalism for the h- dling of many-electron correlation effects. This represents a vivid testimony of a tremendous work that has been accomplished in coupled-cluster methodology and its exploitation.

The Yearn to be Hermitian. - Reduced-Scaling Coupled-Cluster Theory for Response Properties of Large Molecules. - Development And Applications Of Non-Perturbative Approximants To The State-Specific Multi-Reference Coupled Cluster Theory: The Two Distinct Variants. - Development Of Sac-Ci General-R Method For Theoretical Fine Spectroscopy. - Relativistic Four-Component Multireference Coupled Cluster Methods: Towards A Covariant Approach. - Block Correlated Coupled Cluster Theory With A Complete Active-Space Self-Consistent-Field Reference Function: The General Formalism And Applications. - A Possibility For a Multi-Reference Coupled-Cluster: The MrexpT Ansatz. - Eclectic Electron-Correlation Methods. - Electronic Excited States in the State-Specific Multireference Coupled Cluster Theory with a Complete-Active-Space Reference. - Multireference R12 Coupled Cluster Theory. - Coupled Cluster Treatment Of Intramonomer Correlation Effects In Intermolecular Interactions. - Unconventional Aspects of Coupled-Cluster Theory. - Coupled Clusters and Quantum Electrodynamics. - On Some Aspects of Fock-Space Multi-Reference Coupled-Cluster Singles and Doubles Energies and Optical Properties. - Intermediate Hamiltonian Formulations of the Fock-Space Coupled-Cluster Method: Details, Comparisons, Examples. - Coupled Cluster Calculations: Ovos as an Alternative Avenue Towards Treating Still Larger Molecules. - Multireference Coupled-Cluster Methods: Recent Developments. - Vibrational Coupled Cluster Theory. - On The Coupled-Cluster Equations. Stability Analysis And Nonstandard Correction Schemes. - Explicitly Correlated Coupled-Cluster Theory. - Efficient Explicitly Correlated Coupled-Cluster Approximations. - Instability In Chemical Bonds: Uno Cascc, Resonating Ucc And Approximately Projected Ucc Methods To Quasi-Degenerate Electronic Systems.