Abstract:A new viewpoint of computer program poubaix diagram was proposed on traditionalφ-pH diagrams. All equilibrium principle and activity term method were used to plotφ-pH diagrams for M-H₂O systems based on the thermochemical database developed. And a new method———arithmetic-geometric method is used to solve nonlinear equations group. The calculation procedure is proved to be efficient and convergent. The method seldom depends on artificial intervention and can extend to multi-component all equilibriumφ-pH diagrams such as M-ligand- H₂O system.

Key words: Pourbaix diagram; activity term method; all-equilibrium; nonlinear equation group; Pb- H₂O system