Perple_X 07 BUILD prompts



This page is for an out-of-date version (Perple_X 07), the current version (Perple_X 666) page is at perplex_66_build_prompts.

NO is the default ([cr]) answer to all Y/N prompts


In this context, "default" is what Perple_X assumes if the user simply presses the enter key in response to a prompt.

Enter name of problem definition file to be created, < 100 characters, left justified [default = in]:


Perple_X file names may include directory information. The file designated here will be created by BUILD and describes the computation desired by the user. Once created the file can be edited to modify the calculation.

Enter thermodynamic data file name, left justified, [default = hp02ver.dat]:


The thermodynamic data file contains the basic thermodynamic data for all stoichiometric phases and/or species. Typically the files are named XXNNver.dat where XX indicates the authorship or source and NN is the year of the last revision.

The current data base components are:
 NA2O  MGO   AL2O3 SIO2   K2O   CAO  ...
Transform them (Y/N)?


This option would permit the user to redefine the data base components, e.g., to create Fe2O3 from the components FeO and O2.


Component transformations in BUILD are tedious, so if you are going to do many calculations with transformed components the Perple_X program CTRANSF can be used to create a new thermodynamic data file with transformed components. (I think CTRANSF is demonstrated in the Tutorial).

Calculations with a saturated phase (Y/N)?

The phase is: FLUID

Its compositional variable is: Y(CO2), X(O), etc.


Select the independent saturated phase components:

 H2O   CO2

Enter names, left justified, 1 per line, [cr] to finish:


For C-O-H fluids it is only necessary to select volatile species present in the solids of interest. If the species listed here are H2O and CO2, then to constrain O2 chemical potential to be consistent with C-O-H fluid speciation treat O2 as a saturated component. Refer to the Perple_X Tutorial for details.


Saturated phase components are components whose chemical potentials are determined by the assumed stability of a phase, usually a fluid, containing these components.


Typically this option is selected to compute phase relations as a function of the composition of the saturated phase, as in P-T-X(CO2) diagrams that show phase relations as a function of the composition of a fluid that is assumed to be stable.


There are two important implications to specifying a saturated phase: 1) it implies that the phase components are always present in sufficient quantity to saturate the system in the phase; 2) it implies that the specified phase is always stable. Thus, if you are interested in a system with excess H2O, but the physical conditions of the system may be those at which ice is stable you should specify H2O as a saturated component and not as saturated phase. Similarly, if water may not be always present as a pure phase you should specify H2O as a thermodynamic component.

Calculations with saturated components (Y/N)?


**warning ver015** if you select > 1 saturated component, then the order you enter the components determines the saturation hierarchy and may effect your results (see Connolly 1990).


Saturated components are components whose chemical potentials are determined by the assumed stability of pure phase(s) or solutions consisting entirely of  saturated-phase and saturated components.


A system that contains so much silica that a silica polymorph (e.g., quartz or coesite) is stable at all conditions of interest can be specified here by selecting SIO2 as a saturated component. If more than one saturated component is specified Perple_X applies the constraints sequentially, e.g., if AL2O3 and SIO2 are specified as the first and second components, then the excess phases might be corundum + andalusite, if the order is reversed then at the same condition the stable phases would be quartz + andalusite. This sequence is referred to as the saturation hierarchy, see Tutorial Chap 3 for further discussion.  

Use chemical potentials, activities or fugacities as independent variables (Y/N)?


Select < 3 mobile components from the set:
 NA2O  MGO   AL2O3 SIO2   K2O   CAO  ...
Enter names, left justified, 1 per line, <cr> to finish:


If you answer yes to the first prompt you are prompted for the mobile components, i.e., the components whose chemical potentials are to be specified as independent variables.


Diagrams calculated with chemical potentials can be converted to diagrams with fugacities or activities using the program MU_2_F (see perplex_example_6).

Select thermodynamic components from the set:
 NA2O  MGO   AL2O3 K2O   CAO   TIO2  MNO   FEO   ...

Enter names, left justified, 1 per line, <cr> to finish:


Thermodynamic components are components whose chemical potentials are the dependent (implicit) variables of a phase diagram calculation. Phase diagram calculations require the specification of at least one thermodynamic component.

**warning ver016** you are going to treat a saturated (fluid) phase component as a thermodynamic component, this may not be what you want to do.
This warning is given because H2O and CO2 are usually treated as saturated phase components.

Select fluid equation of state:


 0 - X(CO2) Modified Redlich-Kwong (MRK/DeSantis/Holloway) 
 1 - X(CO2) Kerrick & Jacobs 1981 (HSMRK) 
 2 - X(CO2) Hybrid MRK/HSMRK 
 3 - X(CO2) Saxena & Fei 1987 pseudo-virial expansion 
 4 - Bottinga & Richet 1981 (CO2 RK) 
 5 - X(CO2) Holland & Powell 1991, 1998 (CORK) 
 6 - X(CO2) Hybrid Haar et al 1979/CORK (TRKMRK) 
 7 - f(O2/CO2)-f(S2) Graphite buffered COHS MRK fluid 
 8 - f(O2/CO2)-f(S2) Graphite buffered COHS hybrid-EoS fluid 
 9 - Max X(H2O) GCOH fluid Cesare & Connolly 1993 
10 - X(O) GCOH-fluid hybrid-EoS Connolly & Cesare 1993 
11 - X(O) GCOH-fluid MRK Connolly & Cesare 1993 
12 - X(O)-f(S2) GCOHS-fluid hybrid-EoS Connolly & Cesare 1993 
13 - X(H2) H2-H2O hybrid-EoS 
14 - EoS Birch & Feeblebop (1993) 
15 - X(H2) low T H2-H2O hybrid-EoS 
16 - X(O) H-O HSMRK/MRK hybrid-EoS 
17 - X(O) H-O-S HSMRK/MRK hybrid-EoS 
18 - X(CO2) Delany/HSMRK/MRK hybrid-EoS, for P > 10 kb 
19 - X(O)-X(S) COHS hybrid-EoS Connolly & Cesare 1993 
20 - X(O)-X(C) COHS hybrid-EoS Connolly & Cesare 1993 
21 - X(CO2) Halbach & Chatterjee 1982, P > 10 kb, hybrid-Eos 
22 - X(CO2) DHCORK, hybrid-Eos 
23 - Toop-Samis Silicate Melt 
24 - f(O2/CO2)-N/C Graphite saturated COHN MRK fluid
25 - H2O-CO2-NaCl Aranovich and Haefner 2004


Some of the equations of state listed are for specialized applications or for a restricted range of conditions. CORK (5) is a good general purpose EoS that extrapolates well to extreme pressure.


A common mistake in calculations using these equations of state is that users specify a pressure-temperature conditions at which these equations are numerically unstable. As a general rule these equations should not be used at pressure-temperature conditions much lower than the water critical point. They certainly should not be used at zero pressure.

Compute f(H2) & f(O2) as the dependent fugacities (do not unless you project through carbon) (Y/N)?


Answer yes this prompt to describe the fluid with components H2 and O2 instead of H2O and CO2 (Tutorial Chap 6 and Connolly 1995)

Specify computational mode:

     1 - Unconstrained minimization

     2 - Constrained minimization on a grid [default]

     3 - Output pseudocompound data

     4 - Phase fractionation calculations


Unconstrained optimization should be used for the calculation of composition, mixed variable, and Schreinemakers diagrams. Gridded minimization can be used to construct one- and two-dimensional phase diagram sections.


In unconstrained minimization, only thermodynamic potentials (pressure, temperature, chemical potentials) or directly related properties such as the composition of a saturated phase can be chosen as explicit variables. A diagram with no explicit potential variables is a composition diagram, any other diagram is technically a mixed-variable diagrams (potentials and compositions). blah blah.... to be rewritten.






However in Perple_X, diagrams with only one explicit independent potential variable are designated mixed-variable diagrams, whereas as diagrams with two explicit independent potential variables are designated as Schreinemakers-type diagrams if the thermodynamic components are unconstrained and as "phase diagram sections" if the amounts of the thermodynamic components are specified or constrained as a function of a section variable. Refer to the, albeit out-of-date, Perple_X tutorial and examples files for more information about composition and schreinemakers diagrams.


Both modes [1] and [2] can be used for  pseudosection calculations. The default mode [1] (Connolly & Petrini 2002) essentially consists of tracing the edges of each field of a polygonalized pseudosection. The alternative mode [2] is gridded minimization (Connolly 2004?). In gridded minimization the polygonalized pseudosection is mapped from free energy minimizations done on a 1- or 2-dimensional grid, whereby the stable assemblage determined at each grid point is assumed to be stable over the area associated with the grid point. Each mode has features that makes it preferable for certain problems. At least for preliminary calculations I prefer gridded minimization because it is simpler to use and can be run at low resolution to provide rough results quickly. See gridded minimization pros and cons for more complete discussion of advantages of gridded minimization and the grid parameter choices made here. For more information about phase diagram section calculations refer to the seismic velocity, tx_pseudosection, and adiabatic_crystallization tutorials for mode [2] calculations.


For a tutorial on mode [4] calculations refer to the phase_fractionation tutorial.

The data base has P(bar) and T(K) as default independent potentials. Make one dependent on the other, e.g., as along a geothermal gradient (y/n)?


See perplex_tx_pseudosection for an example of a calculation made along a geothermal gradient.

For gridded minimization:


Select x-axis variable:
     1 - P(bars)
     2 - T(K)
     3 - Composition X(C1)* (user defined)
*X(C1) can not be selected as the y-axis variable


In gridded minimization calculations it is possible to construct phase diagram sections as a function of any arbitrarily defined composition (variable X(C1) in this prompt), for example it is possible to make a phase diagram section that shows how the phase relations of a pelitic system would change as its composition is varied by the addition water or a basaltic component. If the user selects X(C1) as a variable, the meaning of the compositional variable is defined in response to later prompts. An example of this type of calculation is in the tx_pseudosection tutorial.

Enter weight amounts of the components:
 SIO2  TIO2  AL2O3 FEO   MGO   CAO   NA2O  K2O   H2O   CO2
for the bulk composition of interest:




Enter molar amounts of the components:
 SIO2  TIO2  AL2O3 FEO   MGO   CAO   NA2O  K2O   H2O   CO2
for the bulk composition of interest:


VERTEX requires the amounts of the components, the units used and total value of the components have no fundamental importance, but define the molar unit for the system. For numerical reasons the weight or molar quantities specified here should not differ by many orders of magnitude from those typical of the phases in the thermodynamic database. Rational molar amounts (1/2, 1, 0, etc.) should be avoided because this is likely to lead a situation in which the composition lies on a tie-line, in such cases there is no unique solution to the phase equilibrium problem.

Enter the plot file name, < 100 characters, left justified [default = pl]:


The name entered here forms the root for various other files generated by subsequent programs.

Exclude phases (Y/N)?

It is simplest to begin by including all possible end-member phases. This allows the user to identify flaws in her perception of what the stable phases should be and/or problems in the thermodynamic data. .


Enter solution model file name [default = newest_format_solut.dat] left justified, <100 characters:


The "solution model file" defines the parameters for the solution phases to be considered in the calculation; these parameters not only specify thermodynamic properties, but also the compositional range and resolution for each solution, i.e., the "subdivision scheme" used by VERTEX to generate pseudocompounds. In order to use Perple_X effectively it is essential to learn how to modify and refine the subdivision schemes specified in the solution model file (for an on-line example see p-t-x pseudosection tutorial, also see chapters 4 and 5 of the Tutorial and the Perple_X technical documentation for more information on subdivision schemes).


Currently, the only up-to-date solution model file at this web site is "newest_format_solut.dat", the subdivision schemes specified in this file are reasonable for the calculation of pseudosections and composition diagrams, but the resolution is too high and should be reduced for most phase diagram projection calculations (Schreinemakers-type diagrams).

Select phases from the following list, enter 1 per line, left justified, [cr] to finish:


The "art" of using Perple_X is in the choice of solution models, the solution model glossary and the commentary within the solution model file itself should be helpful in this regard.


For phases that exhibit immiscibility there are frequently two or more "solutions" that represent different compositional ranges of the same true phase, e.g., Pl, AbPl and AnPl all represent Ca-Na plagoioclase. The reason for this is that in most calculations Perple_X does not test whether coexisting pseudocompounds of the same solution are separated by a miscibility gap. Thus if a single model is used to represent the entire range of plagioclase (i.e., Pl), Perple_X will interpret coexisting albitic (AbPl) and anorthitic (AnPl) plagioclase as being a single phase (See Tutorial Chapters 4 and 5 or Connolly 1990, Connolly & Kerrick 1987, Connolly & Trommsdorff 1991).


A common error, with potentially catastrophic consequences, is that users select both the solution models for the complete compositional range and for the restricted ranges. This causes problems because it has the potential to create a situation in which two or more pseudocompounds have identical properties and therefore Perple_X cannot decide which one is stable. Another bad practice is that users select several different solution models (e.g., Mu and Pheng(HP), both models for potassic mica) representing the same solution. There are situations where this practice makes sense, but if you can't see that for yourself, then the chances are you shouldn't be doing it.