Minimizing Reflections in Electronic Structure Calculations

In electronic structure calculations, large aggregates of atoms are usually approximated by model systems containing far fewer atoms—introducing artificial boundaries that do not occur in the original system. These boundaries ordinarily produce reflected waves that interfere with outgoing solutions of the Schrödinger equation. Depending on the degree of interference, computational results from model calculations may differ widely from the characteristics of the real physical system. Examples of computational studies exhibiting such interference effects abound in many areas of physics. One approach to eliminating the reflection problem is to choose Schrödinger solutions that minimally reflect at the artificial boundary of the model system. These so-called Maximum Breaking of Time-Reversal Symmetry (MBTS) solutions come in pairs that maximally carry current in opposite directions. In effect, by using MBTS solutions, the boundary becomes transparent or nearly-transparent to traveling waves. The MBTS formalism and results for several model systems will be presented.