On the highest order moment closure problem

Macroscopic transport models based on the first six moments of Boltzmann's equation are a natural extension to the drift-diffusion model (two moments) and the various energy-transport models (three or four moments). To close the system of equations the sixth moment has to be expressed as a function of the lower order moments. We investigate the inuence of the applied closure relation on the numerical properties of the six moments model comparing three different methods and propose a new solution to the closure problem. We present results of numerical solutions of six moments models and compare them to self-consistent Monte Carlo data.