Abstract
The recursion method is used to investigate the electronic states of ideal and reconstructed vacancy models in silicon. The matrix elements of the Hamiltonian are taken from Pandey and Phillips, but atoms coupling across the vacancy are treated as first nearest neighbours. The exponential decay factor, beta , for these elements is fitted to self-consistent calculations of the ideal vacancy. The shifts in levels of reconstructed vacancies appear weaker (by up to a factor 2) than those of self-consistent calculations.