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Van der Waals interactions in a dielectric with continuously varying dielectric function
Rudi Podgornik1, V Adrian Parsegian
1Laboratory of Physical and Structural Biology, NICHD, Building 9, Room 1E116, National Institutes of Health, Bethesda, Maryland 20892-0924, USA.
The Journal of Chemical Physics
|October 12, 2004
Summary
This study introduces a new model for van der Waals forces, revealing that continuous dielectric changes can cause both attraction and repulsion between bodies, unlike previous models. The Lifshitz theory is a special case of this new formulation at larger distances.
Area of Science:
- Condensed Matter Physics
- Physical Chemistry
- Materials Science
Background:
- The Lifshitz theory describes van der Waals forces using idealized step-function dielectric profiles.
- Existing models often assume uniform dielectric media and sharp interfaces, limiting their applicability.
Purpose of the Study:
- To formulate and evaluate the van der Waals free energy for a continuously varying dielectric profile.
- To compare this new model with the traditional Lifshitz formulation.
- To investigate the impact of dielectric inhomogeneity on inter-body interactions.
Main Methods:
- Formulation of the van der Waals free energy for a continuous dielectric profile.
- Comparative analysis with the Lifshitz theory, which uses step-function dielectric changes.
- Focus on the free energy component affected by dielectric inhomogeneity.
Main Results:
- The continuous dielectric profile model predicts both attractive and repulsive forces between bodies.
- This contrasts with the original Lifshitz formulation, which typically predicts only monotonic attraction.
- The Lifshitz result is recovered as a limiting case at large separations.
Conclusions:
- Continuously varying dielectric profiles offer a more nuanced understanding of van der Waals interactions.
- The new model explains phenomena not captured by the traditional Lifshitz theory.
- This work extends the applicability of Lifshitz-type theories to more realistic material interfaces.
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