Building blocks of amorphous Ge2Sb2Te5

The structural changes during the phase change between the amorphous and crystalline phase in Ge2Sb2Te5 have been the subject of intense study due to the importance of Ge2Sb2Te5 in phase change memory devices. In our study, the energetics of the transition between the crystalline and the amorphous phase of Ge2Sb2Te5 is explored using density functional theory DFT calculations, electron diffraction, and reverse Monte Carlo model refinement. No energy barrier was found between the crystalline and the previously suggested amorphous structure of Ge2Sb2Te5. Further DFT calculations have led to a different building block of the amorphous structure, which is shown to agree with the experimental reduced density function determined from electron diffraction experiments and previously reported extended x-ray absorption fine structure measurements.