The heights of barriers for the injection of electrons and holes from silicon in SiOx have been calculated in the tight binding approximation without any fitting parameters. The dependence of the electronic structure of silicon-enriched amorphous silicon oxide SiOx on the degree of enrichment has been found. The calculations have been performed with the parameterization of the matrix elements of the tight binding Hamiltonian proposed in our previous work. This parameter involves a change in the localization region of valence electrons of an insulated atom at its introduction into a solid. It has been shown that the inclusion of this change makes it possible to calculate the electronic structure without fitting parameters using the parameters of individual atoms as initial data. This circumstance allows the calculation in the absolute energy scale with zero corresponding to the energy of the electron in vacuum.