  Understanding the structural origins of the properties of amorphous materials
remains one of the most important challenges in structural science. In this
study we demonstrate that local 'structural simplicity', embodied by the degree
to which atomic environments within a material are similar to each other, is
powerful concept for rationalising the structure of canonical amorphous
material amorphous silicon (a-Si). We show, by restraining a reverse Monte
Carlo refinement against pair distribution function (PDF) data to be simpler,
that the simplest model consistent with the PDF is a continuous random network
(CRN). A further effect of producing a simple model of a-Si is the generation
of a (pseudo)gap in the electronic density of states, suggesting that
structural homogeneity drives electronic homogeneity. That this method produces
models of a-Si that approach the state-of-the-art without the need for
chemically specific restraints (beyond the assumption of homogeneity) suggests
that simplicity-based refinement approaches may allow experiment-driven
structural modelling techniques to be developed for the wide variety of
amorphous semiconductors with strong local order.
