Reverse Monte Carlo modeling of amorphous germanium.

Abstract

The reverse Monte Carlo (RMC) method has been used to generate a model for the atomic structure of amorphous germanium (a-Ge). Fitting to experimental neutron diffraction data and applying coordination number and ``triplet'' constraints, the positions of 3000 ``atoms'' in a box, with full periodicity, were altered until the associated model structure factor, S(Q), and pair correlation function, g(r), agreed with the analogous experimental data, within the errors. The model generated is then analyzed to obtain coordination number, bond angle, and ring size distributions. These, in turn, are compared to the results obtained from random network models and other RMC studies. The effects of increasing the number density from the experimentally determined bulk value are also investigated. The results are consistent with an atomic structure which has a characteristic disordered tetrahedral network. For the highest density RMC model, the mean bond angle is 109.4\ifmmode^\circ\else\textdegree\fi{} and the average coordination number is 3.49. \textcopyright{} 1996 The American Physical Society.