# produces a predominance diagram for the Fe-H2O system using the grid approach

  JobTitle                             "Fe-H2O"
  calculationType                      "grid"                                  # uses the 'grid' or brute force approach - slow but more reliable than 'hunt and track'
  calculationMethod                    1
  mainSpecies                          Fe                                      # diagram is for Fe
  xmin                                 2.0                                     # pH range
  xmax                                 12.0
  ymin                                 -90.0                                   # fO2(g) range (controls the redox)
  ymax                                 0.0
  resolution                           101                                     # 101 x 101 grid

  plotTitle                            "Fe-H<sub>2</sub>O<br>(grid approach)"
  xtitle                               pH
  ytitle                               "log <i>f</i> O<sub>2</sub>(g) (atm)"   # this will produce a plot with the native y-scale, fO2(g)
  extraText                            ..\Fe\extratextFeOH.dat                 #   can use the 'yscale' keyword to plot using pe, mV or Eh scales


include ''                                                              # standard file for calculating predominant species
                                                                               #   same as used by the hunt and track approach
   pH        1.8
   units     mol/kgw
   Fe(3)     1e-2
   Na        1e-1
   Cl        1e-1

USE solution 1
   Fix_H+ -<x_axis> NaOH 10                                                    # N.B. this works because <x_axis> is substituted without any leading spaces
     -force_equality true                                                      #   for negative values of <x_axis> would have to form a new tag to avoid --value
   O2(g)  <y_axis> 0.1

   Fe(OH)3(a) 0 0                                                              # the only mineral allowed to form - must be in the database used
END                                                                            #   0 0 means achieve SI=0 and size of initial reservoir is 0 mol Fe(OH)3(a)
                                                                               #   i.e. allow to precipitate but none there to dissolve