Abstract
We present total energy calculations on hydrogenated crystalline silicon as performed by means of a tight-binding semiempirical scheme. The effects of the structural relaxation of the host matrix are computed. Hubbard corrections are found to produce negligible shift in the energy of the cell for each of the interstitial sites here examined. The diffusion behaviour of hydrogen is discussed in the temperature interval between 800K and 1800K as well. We prove that hydrogen diffuses via a jumplike mechanism exploring preferentially regions of high valence charge density. The diffusion coefficient is also numerically estimated and it is shown that at low temperatures it does not fit the Arrhenius extrapolation of the high-temperature data.