Foreword

This Special issue of the Journal of Computational Chemistry is dedicated to the memory of the late Prof. Keiji Morokuma, William Henry Emerson Emeritus Professor of Emory University and Research Leader at the Fukui Institute for Fundamental Chemistry, Kyoto University. Keiji was one of the giants of modern quantum and theoretical chemistry who made numerous fundamental contributions to quantum chemistry and touched the lives and career paths of many scientists. He boldly demonstrated the value of theoretical analysis in broad chemical and biochemical applications. Keiji was one of the rare theoretical scientists who had a deep understanding of theory and algorithms, and at the same time, a true passion for modern and cutting-edge applications in chemistry. He made pioneering contributions to the understanding of intermolecular interactions, developed algorithms to study reaction mechanisms and reaction dynamics of both smalland macro-molecules, and applied theoretical methods to a broad range of problems that included gas-phase molecules in ground and excited electronic states, nanomaterials, biomolecules, as well as homogenous and bio-inspired catalysis. These studies resulted in more than 990 publications, which have garnered more than 47,000 citations during a period that spanned more than five decades. Keiji Morokuma was born in Kagoshima city on July 12, 1934, graduated from Imamiya High School, Osaka (the same High School Prof. Fukui graduated) on March 1953, entered Kyoto University on the same year, and graduated from the Department of Industrial Chemistry (Prof. J. Furukawa’s Laboratory) in 1957. Keiji started his training in theoretical chemistry as a graduate student with the Nobel laureate Kenichi Fukui at Kyoto University, and received his Ph.D. in 1963. He was Research Associate (junior faculty) at Kyoto University from 1962 until 1966. Even during those early days of quantum chemistry when the power of computers was very limited, Keiji started to explore molecular orbital treatment of hydrogen bonds, electronic structure of conjugate molecules, and electron spin resonance spectra of radicals. Great interest in understanding the electronic structure of complex molecules using simple and elegant models was apparent in many of his later studies, even when computations became much more sophisticated and quantitative. Following his graduate study and early training, Keiji moved to the USA to work with future Nobel laureate Prof. Martin Karplus (Harvard University) on reaction dynamics (1966-67). Keiji utilized both quasiclassical trajectories and statistical theories, to study the cross sections of exchange reactions with different modes of activation. As an interesting “side project”, Keiji conducted the first molecular orbital calculation of the water dimer. This study reflected Keiji’s strong interest in understanding the nature of hydrogen bonding interactions, which are of ultimate importance in chemical and biological sciences. In 1967 Keiji joined the Chemistry Department of University of Rochester as an Assistant Professor, and rose rapidly through the ranks, becoming a Full Professor in 1971. During his first independent career, Keiji conducted a series of systematic molecular orbital analyses of hydrogen bonding and donor-acceptor interactions and developed several practical quantum methodologies. These theoretical studies culminated with a landmark paper by Kitaura and Morokuma in 1976, which reported a welldefined decomposition scheme for intermolecular interactions within the molecular orbital (Hartree-Fock) framework. This method allowed, for the first time, a systematic (if not unique) way to dissect intermolecular interactions in terms of physically meaningful components such as electrostatics, exchange repulsion, polarization and charge transfers. The methodology has had a profound impact not only on the understanding of intermolecular interactions, but also on the development of approximate models (e.g., molecular force fields) that describe such interactions in condensed phase and biomolecular applications. The Kitaura-Morokuma analysis also stimulated the development of many other energy decomposition schemes, and the comparison of different methodologies over the years has further deepened our understanding of the nature and subtlety of intermolecular interactions. As a testimony to its impact, the KitauraMorokuma paper published in 1976 is still well cited today, with an annual count of 70-80 citations in the last four years, according to the Web of Science. In 1976, Keiji returned to Japan to lead the newly established Department of Theoretical Studies at the Institute for Molecular Science, Okazaki, Japan. In 1978 he established the Computer Center of the Institute for Molecular Science and was its director from 1978 until 1993. During this period, Keiji worked on a number of other interesting topics,