Theoretica chimica acta

, Volume 68, Issue 6, pp 471–506 | Cite as

Electron difference densities and chemical bonding

  • W. H. Eugen Schwarz
  • Petros Valtazanos
  • Klaus Ruedenberg
Structure
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Accepted:

Abstract

In view of recent advances in X-ray technology it may be possible to deduce information regarding chemical bonding from experimentally determined electron densities. The construction of difference density maps represents a possible intermediate step in attaining this goal, but unresolved questions exist regarding appropriate definitions and interpretations of such maps. To shed light on these problems, theoretical difference densities are determined by ab-initio calculations for the molecules H2, He2, Li2, Be2, N2 and F2 at various internuclear distances. An examination of these difference density maps shows that the identification of those features of molecular electronic densities which are related to chemical bonding requires a judicious construction and a careful analysis of difference densities between molecules and their constituent atoms. Chemically relevant deformations can be small compared to density differences between different components of degenerate atomic groundstates and, consequently, chemical information can be swamped when difference densities are formed with spherically averaged atoms. To avoid such artifacts, oriented unaveraged atomic states must be subtracted for the formation of meaningful Chemical Difference Densities. The latter are explainable by means of a partitioning in terms of contributions from non-bonded inner shells, from lone pairs and from sigma and pi bonding shells. Such partitionings can be obtained through decompositions in terms of natural orbitals from correlated wavefunctions. Canonical SCF orbitals prove to be considerably less effective. Internuclear distances are found to have a great influence upon difference densities regardless of the attractive or repulsive nature of the interactions.

Keywords

Chemical Bonding Difference Density Internuclear Distance Constituent Atom Electron Difference Density 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
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Copyright information

© Springer-Verlag 1985

Authors and Affiliations

  • W. H. Eugen Schwarz
    • 1
  • Petros Valtazanos
    • 1
  • Klaus Ruedenberg
    • 1
  1. 1.Ames Laboratory, USDOE and Department of ChemistryIowa State UniversityAmesUSA

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