Atomic decomposition of Kohn-Sham molecular energies: the kinetic energy component

The decomposition of molecular energies into atomic contributions within Bader's atoms-in-molecules theory is instrumental in rationalising and accounting for not only the stability but also the reactivity of chemical species. Regardless of how it is achieved, it requires the partitioning of the electronic kinetic energy. While this is natural' (but computationally expensive) in the context of wavefunction approaches, it is not more practically straightforward in the framework of Kohn-Sham density functional theory, since the corresponding atomic fictitious (related to the non-interacting system) and correlation components must be calculated. In this paper, we discuss the ability of various approaches, based on either exact formal relationships or previously proposed functional approximations, to estimate them in an efficient way for a wide variety of molecular systems. Such results might pave the way toward the realistic modelling of larger systems of chemical interest and may provide new atomic descriptors to characterise atom types. [GRAPHICS] .