Anharmonic molecular force fields

An anharmonic force field is defined as a higher-order Taylor-series expansion of the molecular potential energy surface (PES) around a reference geometry, usually chosen to be an equilibrium structure. Force field expansions provide excellent local approximations to PESs, one of the most important theoretical constructs of chemistry. This review deals principally with the definition and physical interpretation of anharmonic molecular force fields, their determination via techniques of electronic structure theory, their transformation among different rectilinear and curvilinear representations, and their utilization. Physical and technical factors leading to more precise and more accurate force fields are also discussed. (c) 2011 John Wiley & Sons, Ltd.