(225a) Modeling Nanocolloidal Van Der Waals Forces

The usual route to calculating van der Waals (VDW) forces between colloidal particles is to use Lifshitz theory to obtain the potential energy between two semi-infinite slabs, and then to use these results with the Derjaguin approximation to obtain potential energies between particles. This procedure is usually expected to work well for micron-size colloidal particles; however, for particles less than 10 nm in diameter or dimension, new methods must be developed that account for the discreteness of atoms and the changing dielectric constant. In this talk I discuss our ?coupled dipole method? for obtaining van der Waals forces. This method accounts explicitly for the polarizability of each atom or group of atoms, and by obtaining the eigenmodes of the system of atoms, gives the VDW forces directly. Shortcomings and assumptions of various approaches to calculating VDW forces (e.g., Lifshitz DLP theory, Lifshitz-Derjaguin, Hamaker) will be discussed, along with calculations for various colloidal systems.