Possible unusual atomic arrangements in the structure of amorphous silicon

Insights into the structure of amorphous Si (a-Si) and hydrogenated amorpho us 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 St ructural Database. Out of almost 1800 fragments analysed, a considerable nu mber contain Si atoms in triangular or almost planar square arrangements. I t is suggested that the presence of such configurations in a-Si could accou nt for structure in the first peak of the experimentally determined radial distribution function.