OPTADOS is an open source code to compute Spectral properties. It can run in serial and parallel. It acts as a post-processing tool for CASTEP (and other electronic structure codes). Optados is written by Andrew Morris (Cambridge), Rebecca Nicholls (Oxford), Chris Pickard (UCL) and Jonathan Yates (Oxford). see http://www.optados.org.

wget http://www.castep.org/files/opta_ex.tgz

Helpful Reference

Optados user guide

Latest version http://www.cmmp.ucl.ac.uk/~ajm/optados/