Despite the enormous progress in experimental surface science, notably with spectroscopic
methods exploiting synchrotron radiation and scanning tunneling microscopy, computations
remain one of the most useful sources for accurate data on surface structures. In fact, quite often
it is the combination of experimental and computed results, which gives the most reliable data of
surface structures. As an example, let us apply MEDEA to the Si(001) surface. This surface is the
typical substrate in the manufacturing of semiconducting devices.