MOLECULAR-DYNAMICS SIMULATIONS OF A LARGE STRUCTURE OF AMORPHOUS SI AND DIRECT CALCULATIONS OF THE STRUCTURE FACTOR

There have been a number of simulations of fully bonded models of a-Si containing of the order of 10(2) atoms; comparison was then made with the pair distribution function deduced from neutron and x-ray scattering measurements on Si (or Ge). Obtaining the pair distribution function from the primary data produces a convoluted pair distribution function, and it seems sensible to compute the structure factor so as to make possible a direct comparison with experiment. We have taken the basic model of Wooten, Winer and Weaire and relaxed it slightly to conform to the Stillinger-Weber potential. This is a periodic structure but we have put together 64 such blocks, heated them rapidly to remove the periodicity, then cooled them rapidly to 0 K. The resulting structure factors agree extremely well with experimental measurements.