A procedure to solve the coherent-potential-approximation (CPA) equation for energy- and $k$-dependent self-energies is developed. This version makes it possible to apply the CPA method to cases when the density-of-states curves of the constituent systems differ rather strongly. As a first application the density-of-states curves of the valence band of the mixed system consisting of ${\left(\mathrm{SN}\right)}_x$ and ${\left(\mathrm{SNH}\right)}_x$ linear chains were calculated for hydrogen concentrations between 3 and 50 mole%. The results show a significant effect of the hydrogen impurities on the density of states of ${\left(\mathrm{SN}\right)}_x$.

• Received 3 February 1978

DOI:https://doi.org/10.1103/PhysRevB.18.6460