The exact solution to an electrostatic problem of finding the electric potential of point charges inside a dielectric prolate spheroid is discussed in this note by using the classical electrostatic theory, where the prolate spheroid is embedded in a dissimilar dielectric medium. Such a problem may find its application in hybrid solvent biomolecular simulations, in which biomolecules and a part of solvent molecules within a dielectric cavity are explicitly modeled while a surrounding dielectric continuum is used to model bulk effects of the solvent beyond the cavity. Numerical experiments have demonstrated the convergence of the proposed series solutions.
Keywords
A general electrostatic problemA finite number of point charges are set inside a dielectric cavity of electric permittivity ε i , which is embedded in a homogeneous, isotropic dielectric medium of electric permittivity ε o . The point charges will polarize the surrounding dielectric medium, which in turn makes a contribution, called the reaction field, to the electric field throughout the cavity. The electric field inside the cavity is thus expressed asΨ in = Ψ s + Ψ RF , where Ψ s is the Coulomb potential which can be simply calculated by the well-known Coulomb's Law, and Ψ RF is the reaction field which will dominate the computational cost for calculating the electric field inside the cavity. Such a problem could be encountered in many applications such as hybrid explicit/ implicit solvent biomolecular dynamics simulations [1][2][3]. In particular, in this note we are interested in the exact solution of the problem when the dielectric cavity is either a sphere or a prolate spheroid, and the surrounding medium is either the pure water solvent or an ionic solvent of low ionic strength.By the principle of linear superposition, the electrostatic problem with a single source charge q inside a dielectric cavity only needs to be considered. It is then well-known that the total electric potential Ψ in (r) inside the cavity is given by the solution of the Poisson equation *Tel