We will be making major modifications to your DFT software. At this point, you should create a new copy of all of your octave software in a new directory (called something like ``Solids'') in which to do your work for this assignment.
Expanding the wave functions with an appropriate subset of the full get of basis functions reduces the memory and run-time requirements by a factor of sixteen (in the limit of a large calculation). Fortunately, our software design limits all knowledge of the details of the basis set to the operators O(), L(), cI(), cIdag(), cJ(), cJdag(). Thus, modifying our code to take advantage of reducing the basis set, requires only modification of the corresponding functions (if needed) and of the initialization file ``setup.m''.