Advances in the Theory of Atomic and Molecular Systems

Volume 19 of the series Progress in Theoretical Chemistry and Physics pp 397-415

The Dissociation Catastrophe in Fluctuating-Charge Models and its Implications for the Concept of Atomic Electronegativity

  • Jiahao ChenAffiliated withDepartment of Chemistry, Center for Advanced Theory and Molecular Simulation, Frederick SeitzMaterials Research Laboratory, The Beckman Institute, University of Illinois Email author 
  • , Todd J. MartínezAffiliated withDepartment of Chemistry, Stanford University

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We have recently developed the QTPIE (charge transfer with polarization current equilibration) fluctuating-charge model, a new model with correct dissociation behavior for nonequilibrium geometries. The correct asymptotics originally came at the price of representing the solution in terms of charge-transfer variables instead of atomic charges. However, we have found an exact reformulation of fluctuating-charge models in terms of atomic charges again, which is made possible by the symmetries of classical electrostatics. We show how this leads to the distinction between two types of atomic electronegativities in our model. While one is a intrinsic property of individual atoms, the other takes into account the local electrical surroundings. This distinction could resolve some confusion surrounding the concept of electronegativity as to whether it is an intrinsic property of elements, or otherwise. We also use the QTPIE model to create a three-site water model and discuss simple applications.


Fluctuating charges Charge equilibration Electronegativity equalization Chemical hardness Force fields Molecular models Water models