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Calculation of phase boundary compositions in multicomponent, multiphase systems

for a fixed temperature and pressure

Typically this application might be used for calculating the solubilities of elements in a phase. After having loaded the appropriate data into MTDATA and selected the phase classifications as required, this application is initiated by entering "transn_p.mac". Prompts are provided to help the user to decide what to type in next.

The first prompt asks for the maximum number of phase boundaries to be found. In order to find them all a relatively high number eg 20 should be entered.

Before it is possible to do a calculation, it is necessary to set the temperature required (using the set command) and the compositions limits for the scan. The composition limits are defined through use of composition groups, again using the set command. eg

set "start" = 0.8 0.0001 0.05 0.15 ! set "final" = 0.8 0.05 0.0001 0.15 !

The compositions could be defined either in terms of moles or masses, again by using the set command. eg

set w = 1 !


set n = 1 !

Finally the "range" command is used to confirm these groups and specify the tolerance in composition that we wish to use (typically 0.001). eg

range "start" "final" 0.001 !

The computer output (following the entry of "compute !") for this application consists of:

The initial composition (in terms of moles and masses of the components depending on how it was defined)
The set of phases stable in the particular composition range
The composition of any phase boundaries encountered defined in terms of the proportion of the composition range scanned
    and in terms of the actual component mole or mass fractions
The final composition defined for the calculations

The output might look something like this:

Number of phase boundaries requested 20

Initial component masses
     0.80000000    1.000000E-04    5.000000E-02    0.15000000
GRAPHITE       BCC_A2       M23C6
Boundary mass fraction       0.57463
Boundary composition masses
     0.80000000     2.877427E-02     2.132573E-02     0.15000000
GRAPHITE       BCC_A2       M7C3       M23C6
Boundary mass fraction       0.99061
Boundary composition masses
     0.80000000     4.953120E-02     5.688011E-02     0.15000000
GRAPHITE       BCC_A2       M7C3
Final component masses
     0.80000000     5.000000E-02     1.000000E-04     0.15000000


Updated 7 May 2010