This volume contains review and research articles in one particular ar ea of quantum chemical methodology: the theory of electron correlation and the localization problem. Correlation energy (i.e., the energy be yond the Hartree-Fock) plays an important role in the theoretical desc ription of several chemical processes (reactions, excitations, ionizat ion) while localization in quantum chemistry usually emerges as a math ematical transformation of the wave function. The connection between t hese two issues is provided by the need to evaluate correlation energy for larger molecules, which is...

The aim of this book is to give a simple, short, and elementary introduction to the second quantized formalism as applied to a many-electron system. It is intended for those, mainly chemists, who are familiar with traditional quantum chemistry but have not yet become acquainted with second quantization. The treatment is, in part, based on a series of seminars held by the author on the subject. It has been realized that many quantum chemists either interested in theory or in applications, being educated as chemi ts and not as physicists, have never devoted themselves to taking a course on the...