Structure of liquid phase change material AgInSbTe from density functional/molecular dynamics simulations

The liquid phase of the AgInSbTe phase change material Ag(3.5)In(3.8)Sb(75.0)Te(17.7) has been studied using molecular dynamics/density functional simulations. The calculated structure factor and total pair distribution function agree very well with high-energy x-ray diffraction measurements. We find that: (a) there are signs of medium-range order, (b) Ag and In prefer to be near Te rather than Sb atoms, and promote octahedral coordination in association with Te, (c) Ag is the most mobile element, has the shortest bonds (2.8-2.9 A degrees) and the highest coordination (5.5), and is anionic with the largest effective charge, and (d) there are few cavities (4% of volume).