Section 3: Isolated Intermolecular Interactions10: Intermolecular Interactions in Crystals
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Published:25 Oct 2017
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Special Collection: RSC eTextbook CollectionProduct Type: Textbooks
P. Politzer, J. S. Murray, and T. Clark, in Intermolecular Interactions in Crystals: Fundamentals of Crystal Engineering, ed. J. J. Novoa, The Royal Society of Chemistry, 2017, pp. 375-409.
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The Hellmann–Feynman theorem shows rigorously that noncovalent intermolecular interactions, as in complexes, liquids and molecular crystals, are purely Coulombic in nature. The term Coulombic must be understood to encompass polarization, which includes electronic correlation and dispersion. Other factors that are frequently invoked – such as exchange, Pauli repulsion, orbital interaction and charge transfer – are related to mathematical modeling, not physical reality. Electrostatic potentials computed on molecular “surfaces” can provide considerable insight into intermolecular interactions, but it must be kept in mind that they typically refer to the isolated molecules prior to interaction and hence do not take account of polarization. σ-Hole intermolecular interactions of covalently-bonded hydrogens as well as Group IV–VII atoms are discussed in some detail, as are π-hole interactions.