The authors perform a first-principles cluster calculation of the electronic properties of a-Si using the recursive method in conjunction with the TB-LMTO scheme. The calculated valence band density of states shows good overall agreement with that measured for a-Si by XPS. They find that particular features in the local valence band density of states are not correlated with the surrounding geometric distortions. However, the charge deviations from the mean are proportional to the average local bond angle deviation surrounding the atoms, indicating that local charge transfer in a-Si is mainly due to bond angle distortions.
 

Journal of Non-Crystalline Solids, 97-98 459-62, 1987.