Realistic Inversion of Diffraction Data For an Amorphous Solid: The Case of Amorphous Silicon

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Physics and Astronomy


Mathematics and Natural Sciences


We apply a method called "force-enhanced atomic refinement" (FEAR) ot create a computer model of amorphous silicon (a-Si) based upon the highly precise x-ray diffraction experiments of Laaziri et al. The logic underlying our calculation is to estimate the structure of a real sample a-Si using experimental data and chemical information included in a nonbiased way, starting from random coordinates. The model is in close agreement with experiment and also sits at a suitable energy minimum according to density-functional calculations. In agreement with experiments, we find a small concentration of coordination defects that we discuss, including their electronic consequences. The gap states in the FEAR model are delocalized compared to a continuous random network model. The method is more efficient and accurate, in the sense of fitting the diffraction data, than conventional melt-quench methods. We compute the vibrational density of states and the specific heat, and we find that both compare favorably to experiments.

Publication Title

Physical Review B



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