A concerted rational crystallization/amorphization mechanism of Ge2Sb2Te5

Reverse Monte Carlo refinements using electron diffraction data and density functional theory calculations of the local atomic structure of amorphous Ge2Sb2Te5 confirm presence of a noticeable number of four-membered rings with the general Ge(Sb)TeGe(Sb)Te composition similar to the building blocks of its cubic crystalline phase. The persistence of these rings, as well as the presence of the medium range order at the scale of about 1 nm, suggests that the amorphization/crystallization transition in Ge2Sb2Te5 can be modelled with a concerted rotation of the sheets of atom-squares in {1 0 0} faces of cubic subcells of the cubic crystalline phase, similar to Rubik's cube rotation. This mechanism can produce large models of material that agree with a range of the previous experimental and theoretical studies and also with the experimental electron diffraction data. (C) 2009 Elsevier B.V. All rights reserved.