Parallel band structure calculations

The calculation of the electronic bands in solids can in principle easily be parallelised: the calculation of the energy bands and wave function coefficients at the various $k$ points in the Brillouin zone is independent of each other and can be done on a different processor for each $k$ point. We will illustrate this with the application of the LMTO-ASA band structure code on the Intel i-86O hypercube and also by multitasking for a Cray Y-MP. The implementation follows a master-slaves strategy where the master prepares the potential and charge densities from the wave function coefficients which are provided by the slaves. For practical applications we found it crucial not only to have compute nodes with good floating point operation characteristics, vectorising capabilities and sufficient memory, but also to have access to a fast I/O system for storage of wave function coefficients. An example is given of new possibilities in electronic structure calculations opened up by the increasing availability of parallel computer facilities.