Calculation of stopping powers in ordered ultrathin films

Because v-layer systems with v = 1,2,3,... are the clear laminar limit of nanoscale technologies, predictive calculation of their properties is an important coming need. Strong quantum size effects (QSE) arise in v-layers from the existence of multiple scale lengths (basically thickness and lattice spacing). A simple electron gas argument shows that QSE will be manifest in stopping. The challenge is that modern crystal and film calculations almost always are based on density functional theory in the local density approximation because it usually predicts the energetically favored lattice spacing, symmetry, and cohesive energy well. Contrary to prior usage in stopping theory, the theory provides no wavefunctions and its one-electron energies have known flaws as spectroscopic quantities. In response to these difficulties, we consider some state-dependent local plasma approximations and report the first tests on atoms.