  We present a novel approach for parameter-free modeling of the structural,
dynamical and electronic properties of non-crystalline materials based on
ab-initio Molecular Dynamics, improved signal processing technique and computer
visualization. The method have been extensively tested by investigating
hydrogen and silicon dynamics in hydrogenated amorphous silicon (a-Si:H). By
comparing the theoretical and experimental vibrational spectra we demonstrate
how to relate vibrational properties to the structural stability, bonding and
hydrogen diffusion. We extracted microscopic characteristics that cannot be
obtained by other techniques, namely hydrogen migration and related bond
switching, dangling bond passivation, low hydrogen activation energy, and
a-Si:H stability in general, and we show, via the analysis of a test case, that
our method provides a rigorous and realistic description of non-crystalline
materials. We also demonstrate that this method offers the possibility of
accessing other important macroscopic characteristics of amorphous silicon and
can be used to model all the aspects of a-Si:H dynamics, including the
detrimental Staebler-Wronski effect.
