Possible unusual atomic arrangements in the structure of amorphous silicon

Insights into the structure of amorphous Si (a-Si) and hydrogenated amorphous Si (a-Si:H) have been made by analysing local configurations found in Si fragments in large molecules. The source for this data is the Cambridge Structural Database. Out of almost 1800 fragments analysed, a considerable number contain Si atoms in triangular or almost planar square arrangements. It is suggested that the presence of such configurations in a-Si could account for structure in the first peak of the experimentally determined radial distribution function.