Order-disorder transition in ternary chalcopyrite compounds and pseudobinary alloys

The order-disorder transition in ternary chalcopyrite-structure compounds and related pseudobinary alloys is discussed. An expression relating the critical transition temperature ${\mathit{T}}_{\mathit{c}}$ to the difference in the band gap between ordered and disordered phases Δ${\mathit{E}}_{\mathit{g}}$ is proposed. The results are consistent with the values for ${\mathit{T}}_{\mathit{c}}$ and Δ${\mathit{E}}_{\mathit{g}}$ of these ternary compounds previously reported. In addition, for the isovalent pseudobinary alloys, an order-disorder transition is predicted below about 130 K.