Coupled-cluster theory in atomic physics and quantum chemistry

Abstract

Summarizing the meeting briefly, many quantitative examples were shown which demonstrate the high accuracy of CC methods for electron correlation, compared to otherab initio approaches. Generally, more accurate energies, frequencies and properties of molecules were obtained with less computational effort. Possible exceptions are the problems requiring extensive non-dynamic correlations whose multi-reference character can make large MR-CI calculations superior. Extremely accurate results have also been obtained, even with linearized CC methods, for the (6s–7s) transition moments of cesium, essential to the parity violation problem (Blundell, Sapirstein, Martensson-Pendrill). Attacking yet more difficult problems, CC methods were shown to reliably describe spin lattices (Bishop) and various kinds of model systems (Paldus, Cižek), including the description of phase transitions (Bishop, Arponen). Current CC methods are thus among the most powerful available for many diverse problems, even transcending electronic structure. Moreover, they are being continually improved, e.g. through multi-reference generalizations, a fact that bodes well for the future.