Dispersion Forces
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Feature Article
Full Spec. Ham. Const.
Method Comparison
AFM Force-Distance
From Veels

Hamaker Constants and

London Dispersion Forces

From S. Garofalini

London Dispersion Spectra and Hamaker Constants

bullet vdW and London Dispersion Forces: an Electronic Structure and Chemistry Perspective on Wetting Films, Condensed Matter Seminar Series, Harvard University, April 2000.
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J. Amer. Ceram. Soc. Centennial Feature Article

Full Spectral Hamaker Constant Method

Comparison of Methods To Determine Hamaker Constants

AFM Force-Distance Relationship For Hamaker Constants

Hamaker Constants From Veels

Origins and Applications of London Dispersion Forces in Ceramics: Electronic Structure and Chemistry, Roger H. French, DuPont Co. Central Research, Wilmington DE 19880; Univ. Of Pennsylvania, Materials Science Dept. Philadelphia PA, 19104

    The London dispersion forces are a universal component of long-range vdW forces and arise from the electronic structure of materials and their optical behavior. They play a role in interface and surface energies, wetting, surficial and interfacial films, flocculation of colloidal systems, and force microscopy. These vdW dispersion forces are represented by the Hamaker constant (A), and can be calculated directly from optical property-based electronic structure spectra using Lifshitz theory. Recent access to new experimental and ab initio tools for determination of optical properties of materials has created new opportunities for detailed studies of dispersion forces.

    The close relationship between the London dispersion forces and the materialís chemistry and electronic structure represents an avenue for materials design as has been exploited in ceramics processing and applications. For flocced ceramic systems exhibiting equilibrium intergranular glass films (Igf), such as Pb2Ru2O7 thick film resistors or Si3N4, the Igf thickness results from a force balance where the dispersion force can be varied by Igf chemistry. The interlayer material, the Igf, serves to shield the vdW attraction of the grainís dipoles.

    Finally, new results on the effects of retardation of the London dispersion interaction at large distances are discussed with an emphasis on novel wetting phenomena such as equilibrium surficial films of water on ice and bimodal wetting/dewetting systems.

Comment: (c) 2010 Roger H. French , frenchrh@lrsm.upenn.edu
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