Momentum space properties and local density approximations in small molecules: A critical appraisal

Electron densities obtained from high-quality wave functions are used to assess critically functionals for a variety of molecular properties. We concentrate mainly on those linking the electron density to the moments of momentum, since these relate directly to experimental observables. We also examine exchange and Coulomb functionals, gradient corrections, and information entropies. We determine whether any of the functionals can be considered useful for chemical applications. We examine a range of light molecules near equilibrium geometry, a series of light diatomic hydrides over a range of internuclear distance, and atoms in a range of chemical environments. Closed- and open-shell systems are considered. Large basis sets are used throughout and, for the studies dependent on internuclear separation, we employ correlated wave functions with proper dissociation.