Implicitly charge-conserving solver for Boltzmann electrons

An implicitly charge-conserving algorithm has been developed for solving the nonlinear Poisson equation that results from the use of Boltzmann electrons. The new algorithm solves for the Boltzmann density parameter and, in the case of a Neumann boundary condition, the surface-charge density, simultaneously as it solves for the discretized electrostatic potential. Numerical stability is demonstrated for time steps exceeding the electron plasma period and spatial resolutions much coarser than the Debye length.