Density Functional Theory study of the role of vacancies on the electronic structure in crystalline phase-change materials employing the recently developed KKRnano method on the BlueGene/P supercomputer JUGENE using a cubic supercell of 4096 atoms containing Ge512VAC512Sb1024Te2048. The figure displays the atomically resolved spatial distribution of local density of states (LDOS) at the Fermi energy. In the left lower part the chemical information, in the upper right part the value of the LDOS is displayed. Here, large (small) radii of the spheres correspond to high (low) DOS values. For both parts of the plot Ge, Vac, Sb, and Te are shown in white, transparent, light blue, and dark blue, respectively.