Redefining The Atom: Atomic Charge Densities Produced By An Iterative Stockholder Approach

摘要

One of the main unsolved problems in computational chemistry is the gap between the rigorously defined molecular properties which emerge from first-principles calculations and the more conceptual chemical properties which atoms and functional groups are known to possess, based on scientific experience. In particular, there is no unique method of dividing the electron density of a molecule into a sum of atomic parts.rnPrevious attempts to define atomic electron densities have been unsatisfactory for one or more reasons. Mulliken partitioning, and the related Gaussian Multipoles method based on Distributed Multipole Analysis (DMA), give negative regions of electron density and depend strongly on the basis set used for the calculation. Bader's Atoms in Molecules (AIM) have non-spherical shapes and discontinuous densities. A revised Distributed Multipole Analysis (here referred to as DFT-DMA), or 'fuzzy atoms', based on Density Functional Theory grid integration methods, also give highly non-spherical atoms and depend on arbitrarily chosen atomic radii. Stewart atoms do not reproduce the molecular electron density, and have negative regions of density.