The electron density of a chemical system is probably the most information-rich observable available to chemistry. A topological analysis of the electron density based on the Quantum Theory of Atoms In Molecules provides invaluable chemical information about the bonding interactions and electronic properties. The electron density has the great advantage that it can be obtained either from quantum mechanical calculations as well as experimentally from accurate X-ray diffraction data. This permits a comparison of theoretical and experimental results on an equal footing.
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 doi: 10.1021/acs.jpca.6b06588