  The accuracy of the energy landscape of silicon systems obtained from various
density functional methods, a tight binding scheme and force fields is studied.
Quantum Monte Carlo results serve as quasi exact reference values. In addition
to the well known accuracy of DFT methods for geometric ground states and
metastable configurations we find that DFT methods give a similar accuracy for
transition states and thus a good overall description of the energy landscape.
On the other hand, force fields give a very poor description of the landscape
that are in most cases too rugged and contain many fake local minima and saddle
points or ones that have the wrong height.
