gridhfo.ppi
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# produces a predominance diagram for the Fe-H2O system using the grid approach
SPECIATION
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
PLOT
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
CHEMISTRY
include 'ht1.inc' # standard file for calculating predominant species
# same as used by the hunt and track approach
SOLUTION 1
pH 1.8
units mol/kgw
Fe(3) 1e-2
Na 1e-1
Cl 1e-1
END
USE solution 1
EQUILIBRIUM_PHASES 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
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