Theoretical calculation of Hg–Cd–Te liquidus–solidus phase diagram

Abstract

The liquidus‐solidus phase diagram of Hg‐Cd‐Te is calculated using the pair approximation of the cluster variation method. The work is an exten sion of previous III‐V work and includes association as an additional feature. The liquid phase is approximated by a pseodolattice structure and includes molecular species as well as atomic species. Vacancies are also considered in order to take the pressure effect into account. Unlike the regular solution model, the pair method can take into account the short‐range order in the liquid phase. Adjustable parameters (mostly energies) are first determined to fit Hg‐Te and Cd‐Te binary experiments. The association model can explain the assymetry and the sharp peak at 50% composition. These parameters and several additional ones constitute the one set of parameters (independent of temperature and composition) which are used to calculate the entire ternary liquidus‐solidus diagram Each parameter controls certain features of the diagram. Although the work is stil in progress, reasonably good agreement with known experi ments has ben achieved for both the Hg corner and the Te corner. The chemical potential diagram is discussed.