Electronic structure and band gap composition-dependence of the II-VI   quaternary alloys
  Based on a successful description of II-VI ternary alloys, which introduces an empirical bowing parameter to the widely used virtual crystal approximation, we set up a tight-binding Hamiltonian to describe the Zn_{1-y}Cd_ySe_{1-x}Te_x and Zn_{.9}Cd_{.1}S_{.07}Se_{.93} quaternary alloys. We just use a formula that can be thought as a straightforward generalization of the virtual crystal approximation for this case. Our Hamiltonians reproduce very well the change in the band gap value with the composition observed in recent experimental reports. 
A. E. Garcia, A. Zepeda-Navratil, A. Camacho, D. Olguin and R. Baquero   (Depto. de Fisica, CINVESTAV-IPN, Mexico)