The study of metal‐insulator transitions (MITs) in crystalline solids is a subject of utmost importance, both from the fundamental point of view and for its obvious relevance to the understanding of the transport properties of a vast class of technologically useful materials, including doped semiconductors. This chapter presents the results of NN simulations on the properties of liquid and amorphous GeTe including thermal conductivity and the homogeneous and heterogeneous crystallization of the amorphous. Phase change materials (PCM), recently used extensively in non‐volatile rewritable memory devices, undergo a stable, rapid and reversible transition between a crystalline and an amorphous atomic structure. The coefficients for the Arrhenius function were derived by fitting the simulation results to the experimental data for the crystallization velocity. PCM, and especially Ge‐Sb‐Te (GST) alloys are leading …