Average-atom quantum-statistical cell model for hot plasma in local thermodynamic equilibrium over a wide range of densities

A method for numerically modeling hot plasma over a wide range of densities is described. The model generalizes the essential aspects of the Stewart-Pyatt model to plasmas comprising mixtures of elements and extends the treatment to include the effects of electron polarization and screening. A practical numerical prescription is provided that is a straightforward generalization of the ion-sphere cell model. In addition, exact closed-form expressions are given for the continuum lowering. The model also addresses the problem of the microfield, i.e., the plasma-potential fluctuations that perturb the upper electronic states, and provides a suitable framework for improved practical approaches to this.