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Atomistic simulations on phase-change materials have focused on melt-quenched (MQ) samples, and both system size and quench time have posed challenges. We present here results of massively-parallel density functional (DF) simulations of the as-deposited (AD) amorphous structure of the prototype phase change material Ge2Sb2Te5. We have studied a 648-atom sample generated by computer-aided deposition at 300 K and compare the results with those for a 460-atom MQ sample we reported previously. The AD structure differs from MQ in essential ways:(1) Ge atoms are predominantly tetrahedrally coordinated,(2) homopolar and Ge-Sb bonds are more common and reduce the number of ABAB squares (A= Ge, Sb; B= Te), the characteristic building blocks of the material. The first observation resolves the contradiction between measured and calculated Ge-Te bond lengths, and the latter explains the large differences in crystallization speeds. Sb and Te are more highly coordinated than expected from the “8-N rule”(N is the number of valence electrons), and a-GST cannot be regarded as a covalent network glass.