Abstract:A slightly modified central atoms model was proposed. The probabilities of various clusters with the central atoms and their nearest neighboring shells can be calculated neglecting the assumption of the parameter of energy in the central atoms model in proportion to the number of other atomsi(referred with the central atom). A parameter P_α is proposed in this model, which equals to reciprocal of activity coefficient ofα component, therefore, the new model can be understood easily. By this model, the Al-Zn phase diagram and its thermodynamic properties were calculated, the results coincide with the experimental data.

Key words: central atoms model; diagram calculation; Al-Zn