We have developed a program package GPAW [1] for density functional calculations (DFT) using real-space grids together with the projector augmented wave method. In addition to the basic ground state properties, excited state properties such as optical absorption spectra can be calculated with the time-dependent density functional theory (TD-DFT) where we have implemented both linear response and real-time propagation formulations of the theory.

GPAW is well suited for massively parallel calculations, and we will present current parallelization strategies as well as examples about the parallel scalability. We will present also some examples about the applicability of GPAW
both in DFT and TD-DFT calculations.

[1] wiki.fysik.dtu.dk/gpaw