Model for the structure of amorphous selenium and tellurium

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Abstract
We have constructed and measured by hand a 539-atom model consisting of densely-packed but convoluted chains of covalently bonded, two fold coordinated atoms. There were no rings or interior broken covalent bonds. The model was computer relaxed under potentials that represent bending and stretching of the covalent bonds within the chains and van der Waal's interactions between the chains. The density, the first four peaks in the radial distribution function, and the calculated x-ray and neutron scattering intensities are compared with some success with experimental results on amorphous Se and Te and new insight into their structures is obtained. For example, the peaks in the radial distribution function of both materials can be well understood in terms of two contributions: the first associated with the distribution of atoms in a freely rotating chain, and the second with the dense random packing of spheres.