Two Disordered Phases of the β -Tin Structure in Binary Semiconductors

The Ising model on a beta-tin structure has a phase diagram containing three distinct phases involving order, disorder, and a frustrated ordering. The x-ray crystallographic observation that no ordered beta-tin phases exist at room temperature in compound semiconductors may indicate either "paramagnetic" (dynamic) or frustrated (static) disorder. Density functional pseudopotential calculations determine which regimes real materials fall into and predict that in materials such as GaSb, there may be two temperature-driven transitions between beta-tin structures: from ordered, to frustrated order, to disordered.