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Germaniumtelluride (GeTe) is an iconic functional material, bothin itself and as the parent compound for a range of ternary phase-changedata-storage alloys. Long taken to be a “simple” ABcompound, crystalline GeTe is today known to contain a large numberof germanium vacancies which directly affect the material’smacroscopic properties. Here, we use atomistic simulations to elucidatelocal mechanisms behind the motion of Ge atoms (and thus, vacancydiffusion) in crystalline GeTe. Transition pathways are computed usingthe nudged elastic band (NEB) approach at the gradient-corrected levelof density-functional theory (GGA-DFT), both for the idealized rhombohedral(R3m) crystal and a number of defectiveconfigurations. Besides obvious structural arguments (i.e., beyonda simple rigid-sphere model), the diffusion barriers show a delicatedependence on the material’s electronic structure. The latteris controlled by vacancy formation, Sb adatoms, and charge injection,all of which is discussed in a unified framework. [ABSTRACT FROM AUTHOR]