Quench-rate and size-dependent behaviour in glassy Ge<inf>2</inf>Sb<inf>2</inf>Te<inf>5</inf> models simulated with a machine-learned Gaussian approximation potential

Phase-change memory materials are promising candidates for beyond-silicon, next-generation non-volatile-memory and neuromorphic-computing devices; the canonical such material is the chalcogenide semiconductor alloy Ge2Sb2Te5. Here, we describe the results of an analysis of glassy molecular-dynamics models of this material, as generated using a newly developed, linear-scaling (O(N)), machine-learned, Gaussian approximation potential. We investigate the behaviour of the glassy models as a function of different quench rates (varied by two orders of magnitude, down to 1 K ps-1) and model sizes (varied by two orders of magnitude, up to 24 300 atoms). It is found that the lowest quench rate studied (1 K ps-1) is comparable to the minimum cooling rate needed in order completely to vitrify the models on quenching from the melt