Diagram Example : Tow Dimensional Pourbaix Diagram with Two profile diagrams

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The chemical potential diagram for the Fe-O-H-e- system:

1. Diagram
   
   (1) The Pourbaix diagram in the pH-E/V plot.
   
   
   
   (2)The profile diagram of 5a at the dissection of p(H2) = 1 atm.
   
   
   
   (3)The profile diagram of 5a at the dissection of p(O2) = 1 atm.
   
   
   
   
   
   
2. Description
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   • Default conditions are
     
     • a(H₂O)=1;
       
     • For aqueous species log a=-5 except for water related species.
       
     • Iron containing aqueous species and condensed phases are targetted.
       
     • Condensed phases are shown in solid colored polygons, whereas aqueous species are given in bsDiagCross.
       
     The 5a (1) diagram shows the borderlines of these aqueous species or the condensed phases.
     
     In a normal Pourbaix diagram, the logarithmic concetration of the target element in the aqueous slution can be plotted. Here, however, the thermodynamic activities are used in calcutions. Thus, there can be small differences between two values. For example, we consider Fe2(OH)2+4(a). When Fe2(OH)2+4(a) exists as a = 10^-5. When the total amount of Fe in solution should be calculated, this Fe2(OH)2+4(a) should be acounted as double because two Fe contains in one mole of Fe2(OH)2+4(a). Namely, c(Fe)=2*10^-5.
     
     
   • Dissection data
     
     • Dissection data are shown as the red dashed lines for the conditions of
       
       p(H₂)= 1 atm ;
       p(O₂)= 1 atm ;
       
       For p(H₂)= 1 atm, note that this line passes through a point of
       
       pH=0 and E/V = 0.
       
       This is consistent with the definition of the thermodynamic data of H⁺.
       
       The 5a(1) diagram shows that this line goes through the polygons of
       
       20 Fe+2(a)
       36 Fe3O4(c)
       27 HFeO2-(a).
       
       
       In the 5a(2) profile diagram, those aqueous and condensed phases are shown in the upper part of the diagram. The calculated logarithmic activities of aqueous species show changes in slope at the borderlines of these species.
   
   
3. Details
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   1. [System] MALT

      Search Compounds

   Selection of <Fe,O,H> system with aqueous species
   
   
   
   

   MALT

   Tools > CHD

   with CHD parameter of "/md"

   
   

   2. Run > One Dissection

   Selection of log p(H2) at 0; Check the profile diagram and then the following appears
   
   The profile diagram will appear as the separate diagram given in the separate diagram display panel.
   
   
   3. Selection of log pO2 at 0
      This leads to the formation of the another profile diagram.