Small bond angles in amorphous silicon: are they a new type of defect?

The reverse Monte Carlo structural modeling method and tight-binding molecular dynamics simulations were applied in order to investigate the existence of small bond angles (like those in triangles and squares) in amorphous silicon networks. The influence of small bond angles on the electronic density of states was also analyzed. It is shown that the presence of a small number of bond angles around 75° is necessary for a proper reproduction of the experimental structure factor of vapor deposited amorphous silicon.