Defect-Mediated Relaxation in the Random Tiling Phase of a Binary   Mixture: Birth, Death and Mobility of an Atomic Zipper
  This paper describes the mechanism of defect-mediated relaxation in a dodecagonal square-triangle random tiling phase exhibited by a simulated binary mixture of soft discs in 2D. We examine the internal transitions within the elementary mobile defect (christened the 'zipper') that allow it to move, as well as the mechanisms by which the zipper is created and annihilated. The structural relaxation of the random tiling phase is quantified and we show that this relaxation is well described by a model based on the distribution of waiting times for each atom to be visited by the diffusing zipper. This system, representing one of the few instances where a well defined mobile defect is capable of structural relaxation, can provide a valuable test case for general theories of relaxation in complex and disordered materials. 
Elisabeth Tondl, Malcolm Ramsay, Peter Harrowell and Asaph   Widmer-Cooper
cond-mat.soft